Language, when applied to an Android device, doesn’t just mean the text display: it applies to many other facets. Tap
the ‘Language and input’ option in Settings to access a wide array of language options.
The first lets you change the main text display and activate a spellchecker (tap the settings icon next to it for more options, such as looking up contact names). Also in the main ‘Language and input’ settings, you can choose the keyboard your device uses, set up the text-to speech facility and more.