This might have already been discussed, but I could not find anything like it. I thought it was quite nifty.
If you have a (Unicode) docx that is mainly English (or another Western language) but with Greek words here and there for which you need to set the language in Word to Greek, the link below might help. It leads to a page by Mark Ward, who I think is affiliated with Faithlife.
http://byfaithweunderstand.com/2011/07/29/how-to-find-every-unicode-greek-character-in-microsoft-word/
The technique utilizes the Windows Character Map applet, which is in Win 7 & Win 10 (presumably 8). Macs probably have a similar tool.
In his example, Mr. Ward needed to change the font of Greek words. What I needed to do was set the language to Greek, while leaving the English words as is. Word has an option in the Set Proofing Language dialog "Detect Language Automatically", but I don't think it does what I wanted (it didn't in the document I was working with, anyway)
Instead of changing the font, I used Find & Replace to apply a style I had created. I had set the language on the new style to Greek. I also set the font color to blue, but that was just a way to help me actually see how well it worked. Word instructed me to download and install a Greek language pack, which I did.
The compiled resource enabled Information tool (and double-click) lookup and context menu functionality for Greek lexicons. If anyone needs instructions for the Word style & language settings, let me know and I'll elaborate.