ESL students often have problems in using English conjunctions correctly.

One conjunction is enough to join two clauses - we do not normally use two.

• Though he is poor, he is happy. OR He is poor but he is happy. (NOT Though he is poor, but he is happy.)
• Because I liked him, I helped him. OR I liked him so I helped him. (NOT Because I liked him so I helped him.)

The conjunctions so and yet are sometimes used with and.

• I didn't post that letter, and so she never heard about my illness.

Relative pronouns (e.g. what, which and that) are like conjunctions in some ways: they join clauses like conjunctions do.

• There's the girl who won the prize.

Here the relative pronoun who joins the clauses 'There is the girl' and 'She won the prize'.

A relative pronoun acts as the subject or object of the verb that comes after it. Therefore we do not need another subject or object. In the sentence given above the relative pronoun who is the subject of the verb won.

• I have got a friend who works in a call center. (NOT I have got a friend who he works in a call center.)
• The man that she married was a journalist. (NOT The man that she married him was a journalist.)

The relative pronoun that is often used instead of which, who and whom.

• The man whom / that she married is a friend of mine.

That cannot be used instead of when or where.

• The shop where I work is very small. (NOT The shop that I work is very small.)

But that...in can mean the same as where.