There's no good answer. It's just what we do. In French, why is the plural of "journal" spelled "journaux?" There is a fairly reliable rule that says... well, here's one version: http://www.howtospell.co.uk/y-to-ies-or-s-plural-rule "If the word ends in a vowel (a,e,i,o,u) + y then just add s. boy/boys, journey/journeys, key/keys, tray/trays. b. If the word ends in a consonant + y then y changes to -ies country/countries, baby/babies, body/bodies, memory/memories, sky/skies, variety / varieties" Why? I don't know. I'm afraid English spelling is awful, though--there's never been any attempt to make it phonetic. Learning spelling is a difficult task for native English speakers, and it is so difficult that there is a kind of competitive sport called a "spelling bee" in which high school students compete to see who is best at spelling difficult words.

that's a rule any word end with "y" when you put in plural you replace Y with ies but to use this rule the letter before the Y musn't be one of this " a o e u i " body >> bodies boy >> boys guy >> guys ets