What is the meaning of -aí?

Ending of the plural of certain nouns.

-er (person or thing that does an action indicated by the root verb)

-ist (one who follows a particular ideology; member of a profession or one interested in something; person who uses something)

-ee (person to whom or a thing to which an action is done; person who or a thing that does an action; person who is the other party to a contract)

Added to nouns to form adjectives.

Suffix used to form verbal nouns

Source: wiktionary.org

See also