IPA: /ˌmɒnəˈlɪŋɡwəl/
KK: /mɑnəˈlɪŋɡwəl/
Relating to or knowing only one language.
She is monolingual and speaks only English.
Monolingual → It is formed from "mono-" (from Greek "monos", meaning single or alone) and "lingual" (from Latin "lingua", meaning tongue or language). The word "monolingual" refers to a person or situation involving only one language.
Think of 'mono-' meaning 'single' and 'lingual' relating to 'language' — so a monolingual person speaks only one language.