How to save a unique word

I right clicked on a word to save it as a new word and it turned green but then a few sentences later the same word was there but not in green? I expected it would save that word and whenever I saw it it would be highlighted…

Ok so I guess we can’t do that then.

I don’t know if it’s still a problem, but in the past when I encountered this it was usually due to some punctuation immediately following the word, causing the punctuation to be treated as part of the word (… was one example I remember). I don’t know if this is currently the case, though, I just remember something like that happening a long time ago.

No it was just a word, nothing special about it. I looked at it several times going back and forth, it even had the same dictionary entry when looked up.