A few years ago, we reported that Google really wants you to stick with one language on one page and not mix it up too much.
But I spotted a thread on the Google Webmaster Help where Google's John Mueller said in some cases it is "fine."
There is this webmaster who said that some words on his Spanish web site are better off expressed in English. He wrote:
I use sometimes a word in english while talking in spanish. In a website, for example, I could be interested in ranking for a word as "promoter" inside a content in spanish, because that is how my public understands that concept.
John Mueller from Google responded:
Doing that is fine and not something to worry about.
Obviously, if you are heavily mixing the words on the page, that can be problematic but a word here and there won't do too much damage.
Forum discussion at Google Webmaster Help.
Image credit to BigStockPhoto