subgroups

n.子组

子集.

These subgroups can be recalled for the same match or search, or extracted for post-processing. 这些子组在相同的匹配或搜索中被重复调用，或稍后处理中提取。

Why are matches of subgroups important?The main reason is that there are times where you want to extract the patterns you match, in addition to making a match. 使用圆括号的一个额外好处就是匹配的子串会被保存到一个子组，便于今后使用。