Any pointers on how to know when a hydroxyl group on a molecule will be a base or acid?

I see things like NaOH and that's a base, then I see CH3COOH (acetic acid) but it too has on -OH group on it. Are there any signs to tell if a molecule is an acid or base, because they seem to flip flop a lot. How can I tell if two molecules with -OH group on them is acidic or basic?|||-OH functional groups are called alcohols and they, like water, can be either acids or bases. The rest of the molecule can change that, however. In your two examples, however, the OHs are not functional OH groups and the molecules are not alcohols. Sodium Hydroxide is a base because the OH disassociates as a hydroxide ion, which is strongly alkaline. Acetic acid is acidic not because of its -OH, but because it is a carboxylic acid. The OH is a part of that, but the entire structure is responsible for this behavior.