We can then introduce a new symbol for A {\displaystyle A} ; it's in this way that definitions in ordinary mathematics ultimately work when their statements are reduced to purely set-theoretic terms.
我们可以接着为 A {\displaystyle A} 介入新的符号；普通数学中的定义最终以这种方式工作的，当它们的陈述简化到纯集合论术语的时候。