How many languages can an iPhone display

Yes. Change the language on your iPhone, iPad, or iPod touch - Apple Support

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dvoran wrote:

A non-English speaking or reading person using a smartphone in the US. Can they switch the display language, not just the keyboard?

Regarding the languages in which an iPhone can display its menus and dialogues, see the tech specs item for Language Support. As concerns emails, webpages, documents, messages, etc,, just about every written language covered by Unicode is supported.