猫 = Cat 毛 = Fur 的 is used to indicate the possessive in a similar way to 's in English. 他的猫 = His cat 猫的毛 = The cat's fur 他猫的毛 = His cat's fur For the latter, notice how I didn't write '他的猫的毛'. That's because when you write a series of possessive nouns, you only write 的 once (at the end). Ex. 我的朋友 = My friend 我朋友的爸爸 = My friend's father 我朋友爸爸的猫 = My friend's father's cat 我朋友爸爸猫的毛 = My friend's father's cat's fur There are other times when 的 can be omitted. 的 also has a lot of additional uses in Chinese. Here are a few. ex. 说英语的人 (lit. "speak English 的 people") = people that speak English 吃的 (lit. "Eat的") = Things to eat Adjective的noun 有 (you3) means 'have'. 他有猫 = He has a cat. 他有猫吗? = Does he have a cat? 了, 过 and 以前 are very confusing for English speakers. 了 can be used to indicate a completed action or change of state. It doesn't necessarily represent the past. I think 他爱猫了 is more likely to be 'He now loves cats' (whereas he didn't before), but you'd better ask a native speaker to be sure. 以前 just means 'before'. I recommend you use that here to be safe. I think 他爱过猫 is more like 'He has loved cats'. 了 and 过 can sometimes be extremely confusing. I'd rather a native speaker explained them to you, because I doubt I could do it properly. I'm not sure I translated those sentences correctly in the first place Chinese is typically SVO (subject + verb + object), like English. There are ways to rearrange the word order in Chinese, but in general you should say 他爱猫 instead of 他猫爱.

他有一隻貓 = He has a cat. 我以前喜歡貓 = I used to love cats. 他的貓很大 = His cat is big. 他去了購物 = He went shopping.

I used to love cats. 我原来喜欢猫。 He has a cat? 他有一只猫吗？ He already has two cats. 他已经有两只猫了。

I used to love my cat would be (I previously loved my cat.) So another character might be used to indicate past tense. 了 is more like completed action. 我以前愛我的貓 。。。

One more thing about 了， you can only use了 with action verbs (things you can physically do) which is why it is referred to as completed action. 愛 is not considered an action, just a state of being.