Formal:
* Eloquacious: This implies fluency and grace in speech.
* Articulate: This emphasizes clarity and precision in communication.
* Well-spoken: This is a general term for someone who speaks effectively and with a good vocabulary.
* Learned: This suggests someone who has acquired a lot of knowledge, including a wide vocabulary.
* Erudite: This implies deep learning and scholarship, including a sophisticated vocabulary.
Informal:
* Wordsmith: This is a playful term for someone who is skilled with words.
* Verbal virtuoso: This emphasizes the impressive mastery of language.
* Lexicographer: This is more humorous, as it refers to someone who compiles dictionaries.
* Logophile: This is a fancier term for someone who loves words.
* Polymath: This refers to someone with a broad range of knowledge, including language skills.
Ultimately, the best term depends on the context and your intended meaning.