The plural of aviation, though rarely used since aviation is typically treated as an uncountable noun.
The plural form of 'aviation,' which comes from Latin 'avis' (bird) and the suffix '-ation' describing the act or science of flying, developed as aviation became established in the 1900s.
You'll almost never encounter 'aviations' in real English because aviation is treated as an uncountable noun—we say 'the history of aviation' not 'the histories of aviations,' making this plural form a linguistic curiosity.
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