Noun
(phonetics) A sound occurring between stressed syllables; as the /har/ in philharmonic
(phonetics) A sound occurring between a stressed syllable and the beginning or end of a word; as the o in Deborah.
Source: en.wiktionary.orgAlready in Vulgar Latin intertonic vowels between a single consonant and a following /r/ or /l/ tended to drop: vétulum "old" > veclum > Dalmatian vieklo, Sicilian vecchiu, Portuguese velho. Source: Internet
French, on the other hand, drops even intertonic /a/ after the stress: Stéphanum "Stephen" > Spanish Esteban but Old French Estievne > French Étienne. Source: Internet
Generally, those languages south and east of the La Spezia–Rimini Line (Romanian and Central-Southern Italian) maintained intertonic vowels, while those to the north and west (Western Romance) dropped all except /a/. Source: Internet