MP ~ therefor has one more formal rule than does MP . That is when A B are well-formed formulas then A B is also a well-formed formula .

于是MP°要比MP多一条形成规则：即当A，B为合式公式时，则AB也是 合 式 公式。

That is when A are well-formed formulas then A B is also a well-formed formula .

B也是 合 式 公式。

A logical form is a well-formed formula a structured set of constituents which undergoes formal logical operations determined by its structure .

一个逻辑形式就是一个 完整 的 公式、一套有结构的构成成分以及要经过由其结构决定的形式逻辑运作。