A lessening or reduction in authority, power, or diminishment; the act of making something smaller or less important.
From dis- (negating prefix) plus minion, though the etymology is complex; possibly influenced by Latin minuere (to lessen) combined with dis-; historically rare and possibly confused with similar words.
This is one of English's 'orphan words'—it appeared in a few old texts but never caught on, likely because 'diminution' already did the job better; it's a reminder that not every logically-formed word survives the competition of everyday speech.
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