Neutral:
* Eloquent: This implies the person uses complex language effectively and with skill.
* Learned: This suggests the person has a wide vocabulary and extensive knowledge.
* Well-spoken: This focuses on the person's ability to communicate clearly and effectively.
Negative:
* Pretentious: This implies the person is using big words to show off their intelligence or to sound smarter than they are.
* Pompous: This suggests the person is overly formal and self-important in their language.
* Pedantic: This indicates someone who is overly concerned with details and technicalities, often to the point of being boring or annoying.
Informal:
* Wordsmith: This is a playful term for someone who is good with language, regardless of the complexity of their vocabulary.
The best term to use will depend on the context and the specific impression you want to convey.