下手发球 meaning in English

underarm service
underarm-serve
underhand service

There are three basic kinds of services : the understand serve , the overhand serve , and the hook serve or roundhouse serve
基本上有三种：下手发球、上手发球和钩手发球或抡臂钩手发球。
There are three basic kinds of the underhand serve , the overhand serve , and the hook serve or roundhouse serve
有三种基本的发球方法:下手发球，上手发球和钩手发球或大力(抡臂)钩手发球。
N : there are three basic kinds of services : the understand serve , the overhand serve , and the hook serve or roundhouse serve
基本上有三种：下手发球、上手发球和钩手发球或抡臂钩手发球。