prosthĕsis, is, f., = πρόσθεσις, and prŏthĕsis, is, f., = πρόθεσις,
a grammatical figure consisting in the prefixing of a letter or syllable to a word , prosthesis; as gnatus for natus, tetuli for tuli, Charis. 4; Diom. 2.
·noun The prefixing of one or more letters to the beginning of a word, as in beloved. II. Prosthesi...
Webster's Dictionary of the English Language