The nursery songs usually rhyme at the second and the fourth line,and some even rhyme at all lines.
儿歌：nursery songs 或 children's songs也可,nursery songs是更正式的用语
押韵：rhyme,是不及物动词
句：line,即“行”,英语诗是称作一行行的,而不是一句句（sentence）的,比如最常见的十四行诗sonnet,又称the 14-line verse.