B (be). To exist is to be.
No, the letter 'z' doesn't exist in the Mayan alphabet.
A three-letter word that means "exist" is almost always "are." See if it will work.
exist
Exist
Islands and icebergs exist in the ocean. They begin with the letter I.
exist
exist
dosent exist
dodo
The letter S.
reqium reqium
sentient