1. (用于词头)表示“在…之下”，“在…下面”
Sub- is used at the beginning of words that have ''under'' as part of their meaning.
e.g. The waters were rising about the rock and would soon submerge it.
水快涨到跟岩石一样高了，很快就会淹没它。
e.g. ...a nuclear-powered submarine.
核潜艇
2. (用于名词前构成新名词)表示“次”，“分支”，“部分”
Sub- is added to the beginning of nouns in order to form other nouns that refer to things that are part of a larger thing.
e.g. ...a subcommittee on family values and individual rights.
一个关注家庭价值观和个人权益的小组委员会
e.g. ...the subdivision of farms into smallholdings.
对农田的细分
3. (用于形容词前构成新形容词)表示“低于”，“亚于”，“次于”
Sub- is added to the beginning of adjectives in order to form other adjectives that describe someone or something as inferior, for example inferior to normal people or to normal things.
e.g. The cold has made already substandard living conditions even worse.
寒冷使得已经较差的生活环境变得更糟糕。
e.g. ...educationally subnormal children.
学习能力低下的儿童