I know that the actual pronunciation found in dictionaries is "main-tuh-nence" but I always hear Americans and YouTube videos say it in an American accent and it almost sounds like "Maint-nence" like the "e" part is missing. Do they actually say the e letter but just really fast or skip it ? Thanks!
For many "three syllable words", the unstressed middle syllable is not pronounced in everyday, informal conversation. For example, the following words are pronounced with two syllables:
several (sev rel)
chocolate (chok lit)
Add to this list maintenance (maint nince).
Words such as these are pronounced with three syllables only if the speaker is speaking slowly or very formally and wishes to pronounce all three syllables.