Formal:
* Lexicophile: This is the most precise term, literally meaning "lover of words."
* Logophile: This term emphasizes the love of words in general, not just learning them.
Informal:
* Word nerd: A playful, fun term for someone who enjoys words.
* Word enthusiast: A more general term for someone who is passionate about words.
* Vocabulary aficionado: A slightly more formal way to say someone who loves words.
* Word buff: A casual term for someone who knows a lot of words.
You could also use a descriptive phrase like:
* Someone who loves to expand their vocabulary.
* Someone who enjoys learning new words and their meanings.
Ultimately, the best term depends on the context and the specific personality you want to highlight.