命题是断言某事是或不是事实的陈述。
A proposition is an assertion that something is or is not the case.
世界是一个舞台,我们只是演员。
Sport is part of every man and woman's heritage and its absence can never be compensated for.
当没有人相信你时,你必须相信自己。
The arithmetic of elliptic curves is a microcosm of the deeper structures in number theory.