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a. 1. (Chem. & Physics) Between molecules; situated, or acting, between the molecules of bodies. [ Obs. ] [ 1913 Webster ]

2. Being or occurring within a single molecule; as, intramolecular hydrogen bonds. [ PJC ]

n. Of, pertaining to, or consisting of macromolecules. [ PJC ]

a. [ Cf. F. moléculare. See Molecule. ] (Phys. & Chem.) Pertaining to, connected with, produced by, or consisting of, molecules; as, molecular forces; molecular groups of atoms, etc. [ 1913 Webster ]

Molecular attraction (Phys.), attraction acting between the molecules of bodies, and at insensible distances. --
Molecular weight (Chem.), the weight of a molecule of any gas or vapor as compared with the hydrogen atom having weight of 1 as a standard; the sum of the atomic weights of the constituents of a molecule; thus, the molecular weight of water (H2O) is 18. For more precise measurements, the weight of the carbon isotope carbon-12 is used as the standard, that isotope having the value of 12.000. In this systen, now used almost universally, the hydrogen atom has a weight of 1.0079. [ 1913 Webster +PJC ]

n. (Chem.) An expression representing the composition of elements in a chemical substance, commonly consisting of a series of letters and numbers comprising the atomic symbols of each element present in a compound followed by the number of atoms of that element present in one molecule of the substance. Thus the molecular formula for common alcohol (ethyl alcohol) is C2H6O, meaning that each molecule contains two carbon atoms, six hydrogen atoms, and one oxygen atom. The molecular formula may be written to provide some indication of the actual structure of the molecule, in which case structural units may be written separately. Thus, ethyl alcohol can also be written as CH3.CH2.OH or CH3-CH2-OH, in which the period or dash between functional groups indicates a single bond between the principle atoms of each group. This formula shows that in ethyl alcohol, the carbon of a methyl group (CH3-) is attached to the carbon of a methylene group (-CH2-), which is attached to the oxygen of a hydroxyl group (-OH). A structural formula is a graphical depiction of the relative positions of atoms in a molecule, and may be very complicated. [ PJC ]

n. (Phys. & Chem.) The state of consisting of molecules; the state or quality of being molecular. [ 1913 Webster ]