used to talk about something already known or mentioned
The cat I saw yesterday was black.
我昨天看到的那隻貓是黑色的。
used for the only or main one of its kind
The sun is very bright today.
今天的太陽非常明亮。
used to specify which person or thing you mean
The book on the table is mine.
桌子上的那本書是我的。
used to talk about something in general, not a specific one
The piano is a beautiful instrument.
鋼琴是一種美妙的樂器。
used with adjectives to refer to a group of people or things
We should help the poor.
我們應該幫助窮人。
used before a family name to refer to the whole family
The Smiths are coming to dinner.
史密斯一家要來吃晚餐。
used with units to mean 'every'
She gets paid by the hour.
她按小時計酬。
enough of something for a purpose
I don't have the time to help you.
我沒有時間幫你。
used with time to mean 'the present'
This is the song of the day.
這是今日之歌。
used to show that something is famous or important
She met the president of the company.
她見到了公司總裁。