Opposite of "inter-" is "intra-".
Intraloper, weirdly enough, is a word in use.
"inter-" means between, "intra-" means within, "extra-" means outside. "intra-" and "inter" aren't quite synonyms but they definitely aren't opposites of eachother.
So we have also have the word "extra", but oddly the word "exter" is left out.
I'm exter mad about that.
"inter-" means between, "intra-" means within, "extra-" means outside. "intra-" and "inter" aren't quite synonyms but they definitely aren't opposites of eachother.