You paste a French paragraph into an English document and many ordinary words gain red underlines. Before accepting replacements, inspect the language assigned to that passage. A dictionary for the wrong language can make correct text look defective.
Select only the affected passage
Save a copy, then select the paragraph rather than the whole document. In desktop Word, find Review, Language and Set Proofing Language. In Word for the web, Microsoft documents Review, Editor and Set Proofing Language. Labels differ with interface language and version.
Choose the language the passage actually uses. This setting tells the checker how to interpret the text; it does not translate the paragraph. Changing the language of Office’s menus is a different decision.
Use a short example you can inspect
Try a copied sentence such as Bonjour, merci pour votre message. Assign French and read the suggestions again. In a disposable copy, change Bonjour to Bonjor and check whether the enabled spelling tool flags it. Restore the original sentence afterwards. This is a suggested check, not a claim that we ran your version of Word.
If checking remains absent, inspect whether proofing is disabled for the selection and whether the required language tools are available. Do not hide every warning by switching off checking across the document. Microsoft notes that grammar and writing refinements vary by language.
Preserve a mixed-language document
Keep the main text’s language and mark the inserted passage separately. Inspect the next paragraph too: the selection you changed may have been larger than intended. Finally, reread names, numbers and meaning yourself. Correct language settings make suggestions more relevant; they do not certify that the document is accurate.