| a combining form meaning “same,” used in the formation of compound words: tautomerism. |

| tauto- or taut- pref. Same; identical: tautomerism. [Greek, from tauto, the same, contraction of to auto : to, the; see to- in Indo-European roots + auto, neuter of autos, same, self.] |
tauto- or taut-
pref.
Same; identical: tautomeric.