1. 名詞子句：功用等於名詞，整個子句可作主詞，受詞，或補語。引導名詞子句的連接詞為(a)that，(b)疑問詞(如 when, where, what, how, why, whether, who, which, whom等)。
1. That honesty is the best policy is true. (當主詞)
2. How he will do it is not my business. (當主詞)
3. We don’t know who will get the first prize. (當know之受詞)
4. We are interested in whom he is going to marry. (當in之受詞)
5. They were worried about the fact that you were sick. (當fact之補語)
2. 形容詞子句：形容詞子句的功用等於形容詞，用以修飾前面的名詞，連接詞為who, whom, which, whose等關係代名詞。
1. I discussed it with my brother who is a lawyer. (修飾brother)
2. He is a man whom I won’t trust. (修飾man)
3. This is the book which I bought yesterday. (修飾book)
4. I talked to the woman whose father was a poet. (修飾woman)
(b) 關係代名詞格的判斷要看後面的結構，若結構為“N+____+VP”則空格用主格，若“N+____+S+ VP”則用受格當後面動詞或介系詞之受詞，若“N+____+N”則用所有格。
(c) 在“N+ who +VP”的結構中，V的單複數要與先行詞一致。
(a) 表示“雖然”、“縱然”：though, although, while, even if, even though。
1. Even though it is hard work, I enjoy it.
2. While he has earned a lot of money, he is not happy.
(2) despite與in spite of亦表示“雖然”，但為介系詞，其後應跟名詞片語。
例：Despite ( In spite of ) his illness, he came to the meeting.
(b) 表達“因為”：because, since, as, for, in that。
1. Since you are going, I will go too.
2. My brother didn’t go to school, for he was sick.
3. You should stop smoking in that it’s harmful to your health.
(2) because of為介系詞，其後接名詞片詞。
例：I didn’t go shopping because of the rain.
(c) 表達“目的”：so that, in order that。
1. I packed him a little food so that he wouldn’t get hungry.
2. he studies hard in order that he can pass the exam.
註：表達“目的“之結構尚有“in order to+原形動詞”與“so as to+原形動詞”。
(d) 表達“條件”：If, unless(除非), once(一旦), as long as(只要), on condition that(假如), provided that(假如)。
1. Unless you work harder, you will fail.
2. If it rains, we will stay at home.
3. Once she arrives, we will start.
4. I will lend you the book on condition that you return it on time.
例：Unless I am invited, or I won’t go. (應將or去掉)
(e) 表達“時間”：when, while, as soon as(當), until, since, before, after。
例：1. When I was a child, things were different.
2. He got married as soon as he left university.
3. We won’t start until he comes.
4. We have been friends since we met at school.