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-ator

a combination of -ate1 and -or2 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.

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Compare -tor, -or2.

Origin of -ator

< Latin -ātor, orig. 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 (see -ate1) and a suffix -or (see -or2), and many new English nouns derived from English verbs based on Latin past participles (e.g., vibrator from vibrate)
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019
British Dictionary definitions for -ator

-ator

suffix forming nouns

a person or thing that performs a certain actionagitator; escalator; radiator

Word Origin for -ator

from Latin -ātor; see -ate 1 -or 1
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012