be和become

be:
现在时 I am, you are, he is, we are, you are, they are
（缩略式 I'm, you're, he's, we're, you're, they're）,
（否定缩略式 I'm not, isn't, aren't）, 过去时 I was, you were, he was, we were, you were, they were
（过去时否定缩略式 wasn't, weren't）, 过去分词 been, 现在分词 being
作助动词用，构成各种时态或语态
[与动词的现在分词连用, 构成各种进行时态]
[与及物动词的过去分词连用, 构成被动语态]
[与动词不定式连用, 表示职责、义务、意图、约定、可能性等]
[与不及物动词come, go等的过去分词连用, 构成完成体]
[用be和were表示虚拟语气]

become:
vi.
变成, 成为, 变得
vt.
适合, 相称
区别相当大