IPA: /ˌmʌl.tɪˈlɪŋ.ɡwəl.ɪ.zəm/
KK: /mʌlˈtɪŋɡwəlɪzəm/
The ability to speak and understand multiple languages.
Her multilingualism allows her to communicate with people from different countries.
Multilingualism is formed from "multi-" (meaning many) and "lingua" (from Latin, meaning tongue or language) and the suffix "-ism" (meaning a practice or belief). The word refers to the practice or belief in using or knowing many languages.
Think of 'many' ('multi-') languages ('lingua') being part of a practice or belief ('-ism'). This helps you remember that multilingualism means the ability to use multiple languages.