n.

1. 需要，必要性[U][S1][（+of/for）]
   She felt the necessity of accepting the invitation.

   她感到必须接受这一邀请。

2. 必需品[C][（+of/for）]
   Television is considered a necessity by a lot of people.

   许多人认为电视是一件生活必需品。

3. 必然（性）[U][S1]
   Night follows day as a necessity.

   白天过去，夜幕降临，这是必然的。

4. 贫穷；困难[U]
   This family is in great necessity.

   这户人家穷困到极点。

n.

1. the state or fact of being necessary.
2. an indispensable thing.