魚
さかな · sakana · JLPT N5 · noun
fish
🐟 saka (sake) + na (side dish) = the dish eaten with sake
Etymology: sakana began as 酒菜, saka (sake) + na (side dish), meaning any snack served with drink. Fish was the most common one, so the word came to mean fish itself, replacing the older word uo.
うお · uo · JLPT N3 · noun
fish
🐟 Sounds like whoa! — what you shout when a big fish bites
うお is the older native reading of 魚; everyday speech uses さかな. It survives in compounds like 魚座 (uoza, Pisces) and 魚市場 (uoichiba, fish market). The kanji began as a fish pictograph, and its four bottom dots were once the tail.