The prefix -sub has the meaning of under. It comes from Latin and appears in many English words. The prefix has variants with the same meaning.
The prefix can be found in many words. Examples include submarine, substitute, subterranean, subtitle and subway. A submarine travels under the sea, a substitute works under the regular employer, a subterranean river is located underground, a subtitle is text displayed at the bottom of a screen and a subway travels underground.
The prefix -sub also has variants. They're the result of assimilation. Words with variants of the prefix include suffix, suggest, support, suppress, and surreal.
Here is how the words changed as a result of assimilation:
sub + fix = suffix
sub + gest = suggest
sub + port = support
sub + press = suppress
sub + real = surreal
In these examples we see that the second consonant assimilated the first. This consonant is the trigger and the assimilated consonant is the target. The direction of the assimilation is from right to left. This is also known as regressive assimilation.
Words with the prefix -sub are usually words which have been in the English language for a relatively short period of time. However, those words which have variants such as -suf and -sur are usually words which have been in the English language a long time. Words with assimilation tend to be words which have been in the English language longer than words without assimilation.
Many English words contain the prefix -sub. This common prefix also has variants such as -suf, -sup and -sur. The Greek equivalent of the Latin -sub is -hypo.