What is "zwitterion"

n. (context chemistry English) A molecule, such as an amino acid, that carries both a positive and a negative charge.

In chemistry, a zwitterion ( ; from German zwitter , meaning " hermaphrodite"), formerly called a dipolar ion, is a neutral molecule with both positive and negative electrical charges. (In some cases multiple positive and negative charges may be present.) Zwitterions are distinct from molecules that have dipoles at different locations within the molecule. Zwitterions are sometimes called inner salts.

Unlike simple amphoteric compounds that may only form either a cationic or anionic species, a zwitterion simultaneously has both ionic states.