用法：
1.用作连系动词，其后可接名词、形容词、过去分词等作表语：
He became a teacher at (the age of)17.他17岁就当了老师。
The weather became warmer.天气变得暖和起来。
注意：其后接过去分词时，可表示被动或结果；但表示被动时，其后一般不接by短语。比如不说：
Soon the room became crowded bystudents.
2.become是终止性动词，因此要表示“成为…有多长时间”，英语不能将become与表示一段时间的词或短语连用：
他成为老师有十年了。
正：He became a teacher ten years ago.
正：It’s ten years since he became a teacher.
误：He has become a teacher for ten years.
3.become之后一般不接不定式表示“逐渐…”(此时可用come/begin＋不定式)：
正：He began [came] to like English.他开始喜欢英语起来。
误：He became to like English.
正：He became ill yesterday.他昨天病了。
误：He became to be ill yesterday.
4.用于习语becomeof,表示“发生”、“遭遇”等(常与what连用)：
What has become of the girl?这个女孩后来怎样了?
I don’t know what will become of me if I fail this time.要是我这次不成功，我不知我会怎么样。