序数词用来表名次时前不加冠词the ,那么"Li Ming is the first"为什么first前加the?

序数词用来表名次时前不加冠词the ,那么"Li Ming is the first"为什么first前加the? 序数词前加冠词the吗? first prize前为什么不加the won first prize in his group 是什么意思? 什么时候 first（序数词） 前可以不加the Li Ming is the first _____ (get) to school every day mary was the first in the exam为什么这里要在first前加the呢 序数词的介词如：the first floor前加on还是in? They are in first place.这句话序数词前要不要加the? 序数词前加the? they win first prize.first前要不要加the? first day前要不要加the? first和the first的区别.请顺便讲讲序数词前有无定冠词的区别,