Basic Guidelines For English Spellings
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1Forming nouns denoting the person affected directly or indirectly by the action of the formative verb.
2Forming nouns denoting a person described as or concerned with.
3Forming nouns denoting an object of relatively smaller size.
From Anglo-Norman French -é, from Latin -atus (past participial ending). Some forms are anglicized modern French nouns (e.g. refugee from réfugié).