The noun 鱼 (yú) means "fish" and can refer to the animal or the food. It is a common noun used in everyday conversation about food, cooking, and shopping.
今天晚上我们吃鱼吧。
Jīntiān wǎnshang wǒmen chī yú ba.
Let's have fish for dinner tonight.
这条鱼真新鲜。
Zhè tiáo yú zhēn xīnxiān.
This fish is really fresh.
他最喜欢吃红烧鱼。
Tā zuì xǐhuan chī hóngshāo yú.
His favorite food is braised fish in soy sauce.