Why is “analysises” not the plural of “analysis”?

The plural of analysis is analyses because it’s an irregular plural that doesn’t follow the pluralization rules of regular plural nouns. It’s grammatically incorrect to simply add an “-s” or “-es” to “analysis” and call it “analysises.”

“Analysis” is an irregular plural that follows the Greek pluralization rules, meaning you must change the “-is” at the end of the singular form to “-es” to form the plural.

Scribbr’s free Grammar Checker can help you make sure you’re using the correct plural forms of words.