Interesting, so English language has two words for them. e.g. in Polish both are "małpa" (and usually translated to monkey), similar to turtle and tortoise, for us it is a single world "żółw" (and usually translated to turtle).

Ape could be also translated as "człekokształtne" ("humanoids"?)

It's partly an issue of language, but "old world monkey" and "ape" correspond to specific scientific classifications as well.