A biopolymer is an organic polymer that are typically produced by the cells of living organisms.
biopolymer
A monomer is a submolecule that is proper part of some polymer, and is a building block for such polymer.
monomer
A polymer is a molecule composed of a connected set of monomeric residues.
polymer
A lipid residue is a part of an organic molecule that was derived from a lipid molecule.
lipid residue
A data storage device is a device that is capable of storing information.
data storage device
A solid-state drive (SSD) is a data storage device that uses solid-state memory to store persistent data.
solid state hard drive
A hard disk drive (HDD) is a non-volatile, random access device for digital data. It features rotating rigid platters on a motor-driven spindle within a protective enclosure. Data is magnetically read and written on the platter by read/write heads that float on a film of air above the platters.
hard disk drive
A sound wave is a mechanical wave that is an oscillation of pressure transmitted through a solid, liquid, or gas, composed of frequencies within the range of hearing.
sound wave
chemical group
A chemical functional group is a submolecule that confers specific chemical properties.
chemical functional group
A wave is a physical entity that travels through space and time, consist of oscillations or vibrations and may be accompanied by the transfer of energy.
wave
ncRNA gene
A non-protein coding RNA (ncRNA) gene is a gene that encodes for a RNA transcript that is not further translated into a protein product.
non-protein coding RNA (ncRNA) gene
A chromosome is a molecular complex of circular or linear DNA and bound proteins.
chromosome
A radio receiver is a communication device that receives its input from an antenna, uses electronic filters to separate a wanted radio signal from all other signals picked up by this antenna, amplifies it to a level suitable for further processing, and finally converts through demodulation and decoding the signal into a form usable for the consumer, such as sound, pictures, digital data, measurement values, navigational positions.
radio receiver
The telephone is a communications device that transmits and receives sounds, and are minimally composed of a microphone to speak into, a speaker'which reproduces the voice of the other person and a ringer which makes a sound to alert the owner when a call is coming in.
telephone
A radar is an object-detection system which uses radio waves to determine the range, altitude, direction, or speed of objects.
radar
A device is usually a constructed tool.
device
A communication device is a device that facilitates the transmission of information through encoded in an audio or digital signal between a sender and a receiver.
communication device
A gene that contains an open reading frame which codes for a protein.
protein coding gene
A gene that codes for a functional RNA molecule.
functional rna coding gene
A predicted gene is a gene that was identified through computational method but has not been experimentally validated.
predicted gene
A pseudo gene is a region of a nucleic acid that either cannot be transcribed, or its RNA transcript cannot be translated.
pseudogene
An experimentally validated gene is a gene whose existence has been demonstrated through experimental methods.
validated gene
A sample is a limited quantity of something (e.g. an individual or set of individuals from a population, or a portion of a substance) to be used for testing, analysis, inspection, investigation, demonstration, or trial use.
sample
A liquid solution is a heterogeneous substance in a liquid state.
liquid solution
double stranded nucleic acid is a molecular complex composed of two weakly connected deoxyribonucleic acids.
double stranded DNA
A nucleic acid strand is a single-stranded nucleic acid that is part of a double stranded nucleic acid complex.
nucleic acid strand
forward strand
The positive nucleic acid strand refers to the strand that is to be read 5' to 3'.
positive nucleic acid strand
reverse strand
The negative nucleic acid strand is the strand that is that is complimentary to the forward strand and appears from 3' to 5'.
negative nucleic acid strand
double stranded nucleic acid is a molecular complex composed of two weakly connected nucleic acids.
double stranded nucleic acid
double stranded nucleic acid is a molecular complex composed of two weakly connected ribonucleic acids.
double stranded RNA
A ribosomal RNA gene is a gene that codes for a ribosomal RNA molecule.
ribosomal RNA gene
The 5' splice site is the terminal region of an exon that is 5' to the intron that is to be excised.
5' splice site
The 3' splice site is the terminal region of an exon that is 3' to the intron that is to be excised.
3' splice site
An amino acid is an organic molecule composed of a carbon bonded to four different groups: a carboxyl group, an amino group, an R group, and a hydrogen atom. In the case of glycine, the R group is another hydrogen atom.
amino acid
A cisregulatory element is a DNA sequence located on the same DNA strand or chromosome as the gene whose expression it affects.
cis regulatory element
A trans-regulatory element is a DNA sequence associated with the regulation of a gene located outside the genomic region supporting the corresponding structural DNA region of the trans-regulatory element (i.e., a different DNA strand or different chromosome).
trans-regulatory element
A small cytoplasmic RNA (scRNA) gene is a gene that encodes a small (7S; 129 nucleotides) RNA molecule found in the cytosol and rough endoplasmic reticulum that are normally associated with proteins that are involved in specific selection and transport of other proteins.
small cytoplasmic RNA (scRNA) gene
A small nuclear RNA (snRNA) gene is a gene that encodes a small niuclear RNA molecule.
small nuclear RNA (snRNA) gene
A small nucleolar RNA (snoRNA) gene is a gene that encodes a small RNA that are associated with the eukaryotic nucleus as components of small nucleolar ribonucleoproteins.
small nucleolar RNA (snoRNA) gene
solube RNA (sRNA) gene
tRNA gene
A transfer RNA (tRNA) gene is a gene that codes for a tRNA used in the translation of a messenger RNA (mRNA) to produce a protein product.
transfer RNA (tRNA) gene
scRNA
A small cytoplasmic RNA (scRNA) molecule is a small (7S; 129 nucleotides) RNA molecule found in the cytosol and rough endoplasmic reticulum that are normally associated with proteins that are involved in specific selection and transport of other proteins.
small cytoplasmic RNA (scRNA)
tRNA
A transfer RNA (tRNA) is an RNA molecule that aids in the translation of a messenger RNA (mRNA) to produce a protein product.
transfer RNA (tRNA)
snRNA
A small nuclear RNA (snRNA) is a small RNA molecule that is located in the nucleus of a cell.
small nuclear RNA (snRNA)
snoRNA
A small nucleolar RNA (snoRNA) is a small RNA that are associated with the eukaryotic nucleus as components of small nucleolar ribonucleoproteins.
small nucleolar RNA (snoRNA)
A non-protein coding RNA (ncRNA) is a RNA molecular that cannot be used as a template for generating a protein product.
non-protein coding RNA (ncRNA)
A data collection device is a device that collects information about one or more objects.
data collection device
A mass spectrometer is a device that identifies ions based on their mass to charge ratio using an electromagnetic field.
mass spectrometer
microarray platform
A microarray device is a device that identifies the binding of a target substance to a physically immobile substrate placed in an array or lattice.
microarray device
nuclear magnetic resonance device
A nuclear magnetic resonance (NMR) device is a device that applies a magnetic field to perturb nuclei with an odd number of protons and/or of neutrons in order to hav them absort and re-emit electromagnetic radiation.
nmr device
SNP
SNV
single nucleotide variation
a single nucleotide variation (SNV) is a nucleotide residue that is a variant compared to some reference nucleic acid sequence.
single nucleotide polymorphism
An epimer is a stereoisomer that differs in configuration at only one stereogenic center.
epimer
an analyte is a substance or chemical constituent of interest in an analytical procedure.
analyte
A protein domain is a part of a protein that maintains its structure and function independently of the rest of the protein.
protein domain
a genomic sequence variant is part of a nucleic acid which is compositionally different than another reference genomic part.
variant
genomic sequence variant
A protein coding sequence (CDS) is the region of DNA that is translated to form proteins. The CDS refers to those nucleotides (concatenated exons) that can be divided into codons which are actually translated into amino acids by the ribosomal translation machinery.
CDS
coding sequence
protein coding sequence
A biologic, also known as a biologic medical product, biological, or biopharmaceutical, is any pharmaceutical drug product manufactured in, extracted from, or semisynthesized from biological sources.
biologic
a post-translational modification is a part of a protein that was added, removed, or modified as a result of a chemical reaction after synthesis.
post-translational modification
oligosaccharide
saccharide
a carbohydrate is an organic molecule composed of two or more monosaccharides.
carbohydrate
A microRNA (abbreviated miRNA) is a small non-coding RNA molecule (containing about 22 nucleotides) found in plants, animals and some viruses, that functions in RNA silencing and post-transcriptional regulation of gene expression.
miRNA
microRNA (miRNA)
salt
a chemical salt is a molecular complex composed of an ionic assembly of cations and anions.
chemical salt
a strong chemical salt is a chemical salt that is composed of strong electrolytes. Strong chemical salts contain Na,K,NH4 or NO3, CIO4, CH3COO.
strong chemical salt
a weak chemical salt is a chemical salt composed of weak eletrolytes.
weak chemical salt
a peptide is an organic polymer composed of between two and fifty amino acids.
peptide
an oligopeptide is an organic polymer composed of fewer than 10 or 15 amino acids.
oligopeptide
an amino acid polymer is an organic polymer composed of two or more amino acid residues.
amino acid polymer
an ingredient is a chemical substance that forms part of a mixture.
ingredient
a protein isoform is a protein that is a structural variant (different sequence of amino acids and/or post-translational modifications) of another protein, but encoded by the same gene.
protein isoform
a salt is a heterogeneous substance that is coposed of positively charged ions (cations) and negatively charged ions (anions) held together by electrostatic forces.
A chemical entity is a material entity that pertains to chemistry.
chemical entity
atom, ion, molecule, chemical substance,
A weak submolecular component is a submolecular component that weakly connects submolecular components.
weak submolecular component
A polypeptide is an organic polymer composed of amino acid residues, typically of less than 50 amino acids in length.
polypeptide
A nucleic acid is an organic polymer composed of a sequence of nucleotide residues.
nucleic acid
A ribonucleic acid is an organic polymer composed of a sequence of ribonucleotide residues.
ribonucleic acid
A deoxyribonucleic acid is an organic polymer composed of a sequence of deoxyribonucleotide residues.
deoxyribonucleic acid
A lipid is a water-insoluable organic molecule.
lipid
A submolecular entity is a chemical entity that is a part of a molecule.
submolecular entity
genetic polymorphism is the description of a difference in genetic composition at some location.
genetic polymorphism
A monosaccharide is an organic molecule that consists of a single polyhydroxy aldehyde or ketone group.
monosaccharide
A hydrogen bond is a weak submolecular interaction formed between a hydrogen atom and a electronegative atom.
hydrogen bond
A cation pi interaction is an ionic interaction between the localized negative charge of π orbital electrons, located above and below the plane of an aromatic ring, and a positive charge.
cation pi interaction
A gene is part of a nucleic acid that contains all the necessary elements to encode a functional transcript.
gene
A chemical element is a (effectively) homogeneous substance composed of one type of atom.
chemical element
A drug is a chemical substance that contains one or more active ingredients that regulate one or more biological processes.
drug
A pharmaceutical preparation is a chemical substance that is approved for use in the medical diagnosis, cure, treatment, or prevention of disease.
pharmaceutical drug
A haplotype is one of a set of genomic sequence variants.
haplotype
A protein is an organic polymer that is composed of one or more linear polymers of amino acids.
protein
An atom is composed of a core of protons and/or neutrons which may be surrounded by a cloud of electrons.
atom
A base pair is a weak molecular interaction composed of hydrogen bonds between nucleobases.
base pair
A strong submolecular component is a submolecular component that strongly connects submolecular components.
strong submolecular component
The five prime untranslated region (5' UTR) is a section of messenger RNA (mRNA) and the DNA that codes for it that starts at the +1 position (where transcription begins) and ends one nucleotide before the start codon (usually AUG) of the coding region.
5' untranslated region
A three prime untranslated region (3'-UTR) is the section of messenger RNA (mRNA) that immediately follows the translation termination codon.
3' untranslated region
An organic submolecule is connected region of a molecule.
organic submolecule
An organic molecule is a molecule composed of organic atoms (at least carbon, hydrogen, and optionally oxygen, phosphorus, nitrogen, sulfur)
organic molecule
An open reading frame (ORF) is a part of a gene that encodes a protein but does not contain a stop codon.
open reading frame
An amino acid residue is a submolecule of an amino acid that is part of a larger molecule.
amino acid residue
A nucleotide residue is a part of a molecule that derives from a nucleotide.
nucleotide residue
A poison is a drug that is harzardous or toxic to an organism when ingested at a certain quantity.
poison
An active ingredient is a molecular entity that exhibits biological activity.
active ingredient
An operon is a collection of contiguous genes transcribed as a single (polycistronic) mRNA.
operon
A gene regulatory component is a gene component that exerts a regulatory function.
gene regulatory component
A gene enhancer is a short region of DNA that can be bound with proteins to enhance transcription levels of genes in a gene cluster.
gene enhancer
Aninactive ingredient is a molecular entity that does not exhibit biological activity.
inactive ingredient
A deoxyribonucleic acid template is a deoxyribonucleic acid that provides the template to synthesize a complementary strand of DNA through transcription.
deoxyribonucleic acid template
A deoxyribonucleic acid primer is a deoxyribonucleic acid that enables the synthesis of a complement strand of DNA by binding to it and acting as a point of transcription initiation.
deoxyribonucleic acid primer
An RNA transcript component is a region of an RNA transcript.
RNA transcript component
A mature RNA is a ribonucleic acid that contains an untranslated region (UTR) and protein coding sequence and lacks introns.
mature mRNA
Precursor mRNA (pre-mRNA) is a single strand of messenger ribonucleic acid (mRNA) that is synthesized from a DNA template throught transcription.
pre-mRNA
An mRNA splice variant is an mRNA molecule that varies from another mRNA molecule of the same gene origin but having a different final sequence due to differences in its assembly from splice sites.
mRNA splice variant
A messenger RNA is a ribonucleic acid that contains an untranslated region (UTR) and protein coding sequence and lacks introns.
messenger RNA
A gene that is located on DNA.
dna gene
A gene that is located on RNA.
rna gene
An allele is one of a set of sequence variants of a gene.
allele
A carbohydrate residue is a part of a molecule that was derived from a monosaccharide molecule.
carbohydrate residue
A nucleic acid part is a component of a nucleic acid.
nucleic acid part
A deoxyribonucleotide residue is a part of a molecule that derives from a deoxyribonucleotide.
deoxyribonucleotide residue
A ribonucleotide residue is a part of a molecule that derives from a ribonucleotide.
ribonucleotide residue
A pharmaceutical ingredient is a part of a pharmaceutical preparation.
pharmaceutical ingredient
A chemical complex is a chemical substance composed of weakly connected molecules and ions in a known stoichiometry.
chemical complex
An enzyme is a protein or protein complex that realizes its disposition to covalently modify some molecule during a chemical reaction.
enzyme
A catalyst is a molecule that has the capability to reduce the activation energy of a reaction and hence increase the overall rate of reaction.
catalyst
An organic polymer is an organic molecule composed of connected set of monomeric units.
organic polymer
product
A reagent is a substance that is added to a system in order to bring about a chemical reaction, or added to see if a reaction occurs.
reagent
A specimen is a portion of material for use in testing, examination, or study.
specimen
A buffer is a dissolved chemical substance that resists change in pH upon addition of small amounts of acid or base.
buffer
A solvent is a substance that can dissolve other substances (solutes).
solvent
A solute is a substance that becomes dissolved in a solvent.
solute
An antigen is a molecule that can be bound by a major histocompatibility complex (MHC) and presented to a T-cell receptor.
antigen
A receptor molecule is a molecule that has the capability to bind to a signal and propogate a response to that signal.
receptor
A centrifugation pellet is a solid substance that forms as a result of compaction by a centrifuge.
centrifugation pellet
A supernatent is a liquid substance that remains after centrifugation.
supernatant
A centrifugation substance is a substance that is the target or product of centrifugation.
centrifugation substance
A liquid solution component is a part of a liquid solution.
liquid solution component
A placebo is a medically ineffectual treatment for a medical condition intended to deceive the recipient.
placebo
A ligand is a molecule that is part of a complex by weakly interacting with another molecule.
ligand
A low barrier hydrogen bond is a shorter, stronger hydrogen bond that is formed between both heteroatoms.
low barrier hydrogen bond
A molecular activator is a molecular regulator that realizes its disposition to conformationally change a target molecule and increase its functionality.
activator
A molecular inhibitor is a molecular regulator that realizes its disposition to conformationally change a target molecule and decrease its functionality.
inhibitor
A molecular regulator is a molecule that regulates the function of another chemical entity.
molecular regulator
A signal transducer is a molecule that responds to and amplifies a signal in a signalling system.
signal transducer
A signal is an object that initiates a sequence of events.
signal
A mesenger is a molecule involved in either signal detection or signal propagation from receptors on the cell surface to target molecules inside the cell, in the cytoplasm or nucleus.
messenger
A second messenger is a molecule that relay signals from receptors on the cell surface to target molecules inside the cell, in the cytoplasm or nucleus.
second messenger
A submolecule is any part of a molecule.
submolecule
An intron is a region of a gene that is removed from the final protein open reading frame.
intron
A gene component is a component of a gene.
gene component
An exon is a nucleotide sequence encoded by a gene that remains present within the final mature RNA product of that gene after introns have been removed by RNA splicing.
exon
A gene promoter is a region of DNA that initiates transcription of a particular gene.
gene promoter
A start codon is the first codon of a messenger RNA (mRNA) transcript translated by a ribosome. The start codon is almost always preceded by an untranslated region 5' UTR.
start codon
A stop codon (or termination codon) is a nucleotide triplet within messenger RNA that signals a termination of translation.
stop codon
An RNA transcript is an RNA molecule that is produced from transcription of a nucleic acid template.
RNA transcript
A splice site is a region required for the excision of an intron and connection to another exon.
splice site
An acid is a molecular entity in solution capable of donating a hydron (Bronsted acid) or capable of forming a covalent bond with an electron pair (Lewis acid).
acid
A base is a molecular entity dissolved in a solvent that is capable of accepting a proton (Bronsted base) or forming a covalent bond with a hydron (Lewis base) .
base
An isomer is a molecule that is compositionally identical to another molecule as a result of a different atomic connectivity.
isomer
An ion is an atom or molecule in which the total number of electrons is not equal to the total number of protons, giving it a net positive or negative electrical charge.
ion
An anion is an atom or molecule with a net positive electrical charge.
cation
An anion is an atom or molecule with a net negative electrical charge.
anion
A polar solvent is a solvent that exhibits a polar quality.
polar solvent
A non-polar solvent is a solvent that exhibits a non-polar quality.
nonpolar solvent
A heterogeneous substance is a chemical substance that is composed of more than one different kind of component.
heterogeneous substance
A homogeneous substance is a substance that is composed of a uniform type of entity.
homogeneous substance
An antibody (also known as immunoglobulins, abbreviated Ig) are gamma globulin proteins that are used by the immune system to identify and neutralize foreign objects. They are typically made of two large heavy chains and two small light chains.
antibody
An alpha helix is structural region of a protein that is characterized by 3.6 residues per turn, a translation of 1.5 angstroms along the helical axis in which backbone N-H groups form a hydrogen bond to the backbone carboxyl group of the amino acid four residues prior.
alpha helix
A beta strand is structural region of a protein that is characterized by a roughly planar sequence of amino acid residues forming hydrogen bonds between the N-O and the C=O of another part of the peptide and having their side chains perpendicular to the planar axis.
beta strand
An amino acid polymer submolecule is a submolecule of an amino acid polymer.
amino acid polymer submolecule
An ionic interaction is a weak submolecular interaction between a charged submolecules.
ionic interaction
A protein complex is a molecular complex composed of at least two polypeptide chains.
protein complex
A single bond is a covalent bond between a pair of atoms in which one pair of electrons are shared.
single bond
A double bond is a covalent bond between a pair of atoms in which two pairs of electrons are shared.
double bond
A triple bond is a covalent bond between a pair of atoms in which three pairs of electrons are shared.
triple bond
An aromatic bond is an interaction between a set of atoms across which pairs of electrons are shared.
aromatic bond
A disulfide bond is a bond between two sulfur atoms.
disulfide bond
A dipole-dipole interaction is a weak submolecular interaction between strongly electronegative atoms.
dipole-dipole interaction
van der Waals' interaction is an a weak submolecular interaction between an instantaneous dipole and induced dipole.
van der Waals interaction
A base stack is a stabilizing interaction of DNA and RNA between spatially adjacent nucleotides and possibly involving London dispersion, hydrophobic and electrostatic forces.
base stack
A molecular complex is a chemical complex composed of at least one weakly interacting molecule.
molecular complex
A binary compound is a mereological maximum sum of two kinds of weakly connected entities.
binary compound
A stereoisomer is an isomer in which the atomic connectivity is the same, but differs in its spatial arrangement of atoms.
stereoisomer
A diastereomer is a stereoisomer that is not a mirror image of its isomer.
diastereomer
An enantiomer is a stereoisomer that is a mirror image of its isomer.
enantiomer
An optical isomer is a stereoisomer that rotates the plane of polarization of a beam of plane polarized light.
optical isomer
A structural isomer is an isomer in which the atoms are joined together in different ways.
structural isomer
A ring is a submolecule with a circular topology.
ring
An aromatic ring is a ring in which the electrons are delocalized across all atoms in the ring.
aromatic ring
A heterocyclic ring is a ring containing a hetero atom.
heterocyclic ring
A homocyclic ring is a ring where the atoms are of a single type.
homocyclic ring
An ionic compound is a mereological maximal sum of weakly connected paired positive and negative ions.
ionic compound
An allotrope is a structural variant of a chemical element.
allotrope
A carbon allotrope is a chemical substance composed of carbon.
carbon allotrope
diamond is a carbon allotrope in which each carbon atom in diamond is covalently bonded to four other carbons in a tetrahedron. These tetrahedrons together form a 3-dimensional network of puckered six-membered rings of atoms.
diamond
graphite is an allotrope of carbon which is a conductor, and is the most stable form of solid carbon.
graphite
fullerene is a carbon allotrope which take the form of a hollow sphere, ellipsoid, or tube.
fullerene
aggregate of carbon nanorods is an allotrope of carbon considered to be the least compressible material known, as measured by its isothermal bulk modulus; aggregated diamond nanorods have a modulus of 491 gigapascals (GPa), while a conventional diamond has a modulus of 442 GPa. ADNRs are also 0.3% denser than regular diamond.
aggregated carbon nanorods
amorphous carbon is an allotrope of carbon that does not have any crystalline structure. As with all glassy materials, some short-range order can be observed, but there is no long-range pattern of atomic positions.
amorphous carbon
carbon nanofoam is an allotrope of carbon that consists of a low-density cluster-assembly of carbon atoms strung together in a loose three-dimensional web. Each cluster is about 6 nanometers wide and consists of about 4000 carbon atoms linked in graphite-like sheets that are given negative curvature by the inclusion of heptagons among the regular hexagonal pattern.
carbon nanofoam
chaoite is an allotrope of carbon that is slightly harder than graphite with a reflection colour of grey to white.
chaoite
glassy carbon is an allotrope of carbon which is widely used as an electrode material in electrochemistry, as well as for high temperature crucibles and as a component of some prosthetic devices.
glassy carbon
ionsdaleite is a hexagonal allotrope of the carbon allotrope diamond.
ionsdaleite
boron atom
carbon atom
hydrogen atom
helium atom
lithium atom
beryllium atom
nitrogen atom
oxygen atom
fluorine atom
neon atom
sodium atom
magnesium atom
aluminium atom
silicon atom
phosphorus atom
sulfur atom
chlorine atom
argon atom
potassium atom
calcium atom
scandium atom
titanium atom
vanadium atom
chromium atom
manganese atom
iron atom
cobalt atom
nickel atom
copper atom
zinc atom
gallium atom
germanium atom
arsenic atom
selenium atom
bromine atom
krypton atom
rubidium atom
strontium atom
yttrium atom
zirconium atom
niobium atom
molybdemum atom
technetium atom
ruthenium atom
rhodium atom
palladium atom
silver atom
cadmium atom
indium atom
tin atom
antimony atom
tellurium atom
iodine atom
xenon atom
caesium atom
barium atom
lanthanum atom
hafnium atom
tantalum atom
tungsten atom
rhenium atom
osmium atom
iridium atom
platinum atom
gold atom
mercury atom
thallium atom
lead atom
bismuth atom
polonium atom
astatine atom
radon atom
francium atom
radium atom
actinium atom
rutherfordium atom
dubnium atom
seaborgium atom
bohrium atom
hassium atom
meitnerium atom
darmstadtium atom
roentgenium atom
copernicium atom
unutrium atom
ununquadium atom
ununpentium atom
ununhexium atom
ununseptium atom
ununoctium atom
cerium atom
praseodymium atom
neodymium atom
promethium atom
samarium atom
europium atom
gadolinium atom
terbium atom
dysprosium atom
holmium atom
erbium atom
thulium atom
ytterbium atom
lutetium atom
thorium atom
protactinium atom
uranium atom
neptunium atom
plutonium atom
americium atom
curium atom
berkelium atom
californium atom
einsteinium atom
fermium atom
mendelevium atom
nobelium atom
lawrencium atom
A covalent bond is a strong submolecular interaction between atoms.
covalent bond
A molecule is a single chemical entity composed of fully covalently bonded atoms.
molecule
mixture
A chemical substance is a chemical entity composed of two or more weakly (non-covalently) interacting chemical entities.
chemical substance