clauses

Clause 4 of the constitution is thought to be the most important section.

宪法第四条被认为是最重要的部分。

In the sentence "I'll get you some stamps if I go to town", "if I go to town" is a subordinate/dependent clause (= it is not as important as the main part of the sentence and could not exist as a separate sentence).

在 I'll get you some stamps if I go to town（如果我去城里，会给你带些邮票）这句话中，if I go to town 是从句／从属分句。