There are two commonly used: "sub-" and "under-" itself.
e.g. "substandard", "subway", "subordinate" etc.
"understatement", "underpass", "underwear" etc.
"sub" is the Latin word for "under".
sub
Sub- Subterranean Submit submarine subsurface
That would be 'sub'.
Hypo Sub (submerge, subordinate, subhuman)
The latin Prefix 'Sub' can mean 'under', 'beneath', or 'below' (such as in the Word 'Subconscious'), 'inferior to', or 'part of' (such as in the Word 'Subhuman'), 'less than normal' (such as in 'Substitute'), or 'almost/nearly' (such as in the Word 'Subcentral').
'Sub' as in 'subhuman' would do or 'hypo' as in hypodermic the latter meaning under the skin. Don't confuse hypo as a prefix with hyper; there is a major difference between someone who is hypoglycaemic and hyperglycaemic. .....................................................................................................................
The prefix is sub- (meaning underneath or below), the suffix is -ous (meaning to pertain to) and the root word is -cutane- meaning skin. The word subcutaneous means pertaining to beneath the skin.
The root word for submerge is "merge," which means to combine or blend. The prefix "sub-" means under or beneath, so submerge means to put something below the surface of water or liquid.
Inter is a prefix meaning 'between'.
Infra- and Under- are prefixes for beneath. Please correct this if wrong.
The prefix hypo- means under, beneath, or low So hypothermia means low body temperature, and a hypodermic syringe inserts its contents below the skin.
The prefix "hypo-" means below, beneath, or less than normal.
The Latin prefix 'infra' means 'under', as in infrastructure, infrared, infra dig, inferior, etc.
under means below or beneath
In the term "subcutaneous", the prefix "sub" means "under" or "below". A standard prefix in English, "sub" derives most immediately from Latin and is also found in such common terms as "subterranean", "substitute", "submarine", and "substandard", among many others.