Monolingual v. Unilingual

A Reuters article just used the word 'monolingual'. Perhaps I am being neurotic, but I cannot accept this as a word. The word should be 'unilingual'. A quick review of combining forms:
English : one, Greek : mono-, Latin : uni-
English : tongue, Greek : -glot-, Latin : -ling-

To mean 'under the tongue', doctors say 'sublingual' or 'hypoglossal', not 'subglossal' or 'hypolingual'. Although, should words derived from Greek end with 'al'? I think 'hypogloss-' was imported into Latin, and thus qualifies for the -al suffix. Not that I really care about that though.

Of course, 'monocle' is guilty of the same thing. As well as a number of words that I use everyday. So I'm a subcrite. Get over it.