molecule
A substance that has two or more atoms chemically bonded together. Examples are H2, H2O, N2, O2, etc. Remember, a molecule is formed by as least two or more ATOMS, so a single oxygen atom (O) is not a molecule.
Sometimes, molecule and compound are very hard to distinguish, for example, H2O (aka water) can be both a molecule AND a compound.
Sometimes, molecule and compound are very hard to distinguish, for example, H2O (aka water) can be both a molecule AND a compound.