The what3words API supports 37 languages with more being added all the time. These currently include: English, French, Spanish, Portuguese, Russian, Swahili, German, Turkish, Swedish, Italian, Mongolian, Arabic, Finnish, Polish, Danish, Norwegian, isiXhosa, isiZulu, Greek, Dutch, Czech, Afrikaans, Bahasa Indonesia, Japanese, Korean, Thai, Chinese, Hindi, Bengali, Tamil, Telugu, Marathi, Bahasa Malaysia, Hungarian, Romanian, Hebrew and Bulgarian. You can call the what3words API to find out the available languages programmatically using the available-languages function.
Learn how here.