Word doesn't correctly detect my language
The text may contain a mixture of languages. Microsoft Word evaluates text sentence by sentence to determine its language. If a sentence contains words from more than one language, or many scientific or other special terms, Word may apply the default language for the document or it may apply the language of the preceding sentence.
If a word has a wavy underline because it is in a different language, you can apply the correct language. Right-click the word, point to Language on the shortcut menu, and then click the language you want.
The language Word detected may be only subtly different from another language, for example Norwegian and Danish or Spanish and Portuguese. When languages have subtle differences in spelling, Word may not be able to identify the correct language, especially if there are only a few words in the sentence.
If you have two similar languages enabled for editing and you only write in one of these languages, try to disable the language you don't use.
If none of the above result in correct language detection, you can apply the language format manually (Tools menu, Language submenu, Set Language command).
Word doesn't detect my language at all
The language may not be supported by Microsoft Word.
Languages Word can detect automatically