One of the very small invisible particles of which all matter is supposed to consist.
The smallest part of any substance which possesses the characteristic properties and qualities of that substance, and which can exist alone in a free state.
A group of atoms so united and combined by chemical affinity that they form a complete, integrated whole, being the smallest portion of any particular compound that can exist in a free state; as, a molecule of water consists of two atoms of hydrogen and one of oxygen. Cf. Atom.
The magnitude of the atomic weight determines the character of the element, just as the magnitude of the molecule determines the character of a compound body. Dmitri Mendeleev
It now seems certain that the amino acid sequence of any protein is determined by the sequence of bases in some region of a particular nucleic acid molecule. Francis Crick
The detailed geometry of the coenzyme molecule as a whole is fascinating in its complexity. Dorothy Hodgkin
Nanotechnology is the idea that we can create devices and machines all the way down to the nanometer scale, which is a billionth of a meter, about half the width of a human DNA molecule. Paul McEuen
Three things about water affect almost all of cooking. First are the hydrogen bonds, which is why it has an incredibly high boiling point. Another is that it's a polar molecule, so that it dissolves a lot of things, and there are things that won't mix with it. And then there's how much energy it takes to heat water. Nathan Myhrvold