If someone who can speak three language we call Trilingual ,2 language - Bilingual ,How about someone who Only can speak one language?

Monolingual

Monoglot, just as one who speaks several is a polyglot. We use "bilingual" for speaking two languages because English uses Latin words for things that are relatively common. Although the inability to speak more than one language is extremely common, it is in fact so common that we rarely need a word for it, and any word we very seldom use is, by English custom, taken from Greek.

Onelingual lol

no but seriously I just checked and some are saying it's monolingual and unilingual

monoglot, just as one who speaks several is a polyglot... we use "bilingual" for speaking two languages 'cause english uses latin words for things that are relatively common... although the inability to speak more than one language is extremely common, it is in fact so common that we rarely need a word for it, and any word we very seldom use is, by english custom, taken from greek...

Monolingual or unilingual describes someone who only speaks one language.

https://en.wikipedia.org/wiki/Monolingualism

onelingual lol

no but seriously i just checked and some are saying it's monolingual and unilingual

Unilingual monolingual sololingual homolingual

Americans! That was a joke with some foreign friends and me.

americans! that was a joke with some foreign friends and me...