You can add words to the dictionary or use the language dialog to choose a language for the selected text. Go to Review > Language > Set Proofing Language. Note: Languages in use in the document display at the top. Languages with downloaded proofing tools have a checkmark symbol. More @Wikipedia
Hover over any link to get a description of the article. Please note that search keywords are sometimes hidden within the full article and don't appear in the description or title.