'Be' 可以既是主要动词也是助動詞，并且在这两种角色中都是不规则动词。作为主要动词，'be' 用于描述主语的状态或条件。它可以表示存在和位置。作为助動詞，它用于构成进行时态并指代正在进行的动作。它有以下几种形式：
一般现在时
I
am (我 是)
you
are (你 是)
he/she/it
is (他/她/它 是)
we
are (我们 是)
you
are (你们 是)
they
are (他们 是)
示例You are a lawyer.
你是律师。
(主要动词)
He is singing.
他在唱歌。
(助動詞)
一般过去时
I
was (我 是)
you
were (你 是)
he/she/it
was (他/她/它 是)
we
were (我们 是)
you
were (你们 是)
they
were (他们 是)
示例He was sad.
他很伤心。
(主要动词)