What is a defining feature of an organic acid?

A defining feature of an organic acid is that it contains one or more carbon atoms. Organic acids are a subset of acids characterized by their carbon-based structures, which typically include a carboxylic acid group (-COOH) that is responsible for their acidic properties. This structural feature distinguishes them from inorganic acids, which may not contain carbon.

While organic acids can vary in their strength—some can be strong acids, but many are weak—this aspect does not define them as organic acids. Furthermore, while many organic acids do tend to donate one proton, there are organic acids capable of donating multiple protons based on their functional groups. Therefore, the presence of carbon atoms is the fundamental characteristic that classifies a substance as an organic acid.