1.
Sub- is used at the beginning of words that have ‘under’ as part of their meaning.
The waters were rising about the rock and would soon submerge it.
...a nuclear-powered submarine.
PREFIX
2.
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.
...a subcommittee on family values and individual rights.
...the subdivision of farms into smallholdings.
PREFIX
3.
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.
The cold has made already substandard living conditions even worse.
PREFIX