Most people use 3 word addresses in their native language.
If you are German and want to use what3words to tell other Germans about addresses in Mexico, you can use ///anruf.kostenlos.seehöhe – a spot just outside Mexico City. But equally you might see the address in English, or Spanish in a guidebook.
In the app, if you want to use a language other than English (UK) you will need to download a small file (about 6MB) containing the wordlists and speech recognition software for that language. The language packs are downloadable separately to reduce the overall size of the app.