-ator

1. a combination of -ate ¹ and -or ² that forms nouns corresponding to verbs ending in -ate1 ,denoting a human agent ( agitator; mediator; adjudicator ) or nonhuman entity, especially a machine ( incubator; regulator; vibrator ) performing the function named by the verb.

-ator

suffix forming nouns

1. a person or thing that performs a certain action

   agitator

   escalator

   radiator

Word History and Origins

Origin of -ator¹

< Latin -ātor, originally not a suffix, but the termination of nouns formed with -tor -tor from verbs whose stems ended in -ā-; in English, Latin loanwords ending in -ātor have been reanalyzed as derivatives of the past participles in -tus ( -ate ¹ ) and a suffix -or ( -or ² ), and many new English nouns derived from English verbs based on Latin past participles (e.g., vibrator from vibrate )

Word History and Origins

Origin of -ator¹

from Latin -ātor; see -ate ¹-or ¹