vegetarano

Cut it at the seam and it decodes itself. Vegetar plus -an- plus -o: the suffix that makes a member or an adherent of something, the same one behind kristano, urbano, klubano and kongresano. A vegetarano is one of the vegetarian party. Esperanto did not borrow the English word whole; it borrowed the stem and let its own machinery finish it, which is why the adjective is vegetara and a vegetarian dish is vegetara manĝo.

Do not say vegetariano. That is the reflex of every speaker of a European language and it is one syllable too long, because the -ian of the English word is doing the job -an- already does here. The same trap sits in bibliotekisto and elektristo: take the international stem, then use the Esperanto suffix, not both.

A vegano is the stricter case, and Esperanto took that word whole from English rather than deriving it, so the two do not pattern together the way their English versions do. If you need to be exact about eggs and milk, say so: mi manĝas ovojn sed ne viandon settles the question faster than any label.