I'M, contracted from I am.
IM, in composition, is usually the representative of the Latin in; n being changed to m, for the sake of easy utterance, before a labial, as in imbibe, immense, impartial. We use the same prefix in compounds not of Latin origin, as in imbody, imbitter. For im, the French write em, which we also use in words borrowed from their language.
