A bilingual Word document may need an English introduction followed by a French quotation. Giving the entire document one proofing language can make one passage easier to check while assigning the wrong language to the other. Treat the language as a property of the intended text range.

Work in a copy containing two clearly separated paragraphs whose languages you know. Label them in your working notes as Passage A and Passage B, and record the intended language for each. Keep the wording intact while you investigate its selection scope.

Assign each passage separately

In desktop Word for Windows, select only Passage A and open Review, Language, Set Proofing Language. Choose its intended language. Microsoft identifies installed proofing tools with a checkmark; if the required tools are missing, inspect Language Preferences. Do Not Check Spelling or Grammar suppresses checking rather than selecting a different dictionary.

Next select only Passage B and assign its own language through the same dialog. Avoid Select All for this correction: the task is to keep two different language assignments in the same document. Check the visible selection before confirming each change, especially where a quotation begins midway through a paragraph.

Reselect Passage A and inspect its language again. Then reselect Passage B and repeat. Confirm the two assignments individually instead of inferring them from which words currently have underlines. If one was changed unexpectedly, correct the selection boundary before continuing through the document.

Handle short passages deliberately

Microsoft notes that automatic detection may need one or several sentences and can be confused by words shared across languages. A short fixed label or a quotation inside another language therefore deserves an explicit selected-text check rather than an assumption that detection will identify it correctly.

Add a small temporary continuation to Passage A in the working copy, then inspect that new text's proofing language and the neighbouring Passage B. Remove the trial afterwards. This tests the editing pattern you will actually use without substituting a whole-document language change.

Before delivery, revisit passages that were pasted or substantially rewritten and verify their intended language ranges. Selecting a proofing language does not translate the wording or establish that a quotation is accurate. The acceptance result is two correctly scoped language assignments that remain understandable during later editing.

Sources: Microsoft: proofing languages; Microsoft: automatic language detection.