Neutral:
* Eloquent: This describes someone who speaks or writes clearly and effectively, using refined language.
* Articulate: This describes someone who can express themselves clearly and effectively.
* Well-spoken: This describes someone who uses language grammatically and effectively.
Positive:
* Learned: This describes someone with extensive knowledge and a wide vocabulary.
* Erudite: This describes someone with deep knowledge and a wide range of interests.
* Sophisticated: This describes someone who is cultured and refined in their speech and manner.
Negative:
* Pretentious: This describes someone who uses sophisticated language to appear more intelligent than they are, often in a way that is annoying or off-putting.
* Pompous: This describes someone who is excessively self-important and uses language to show off.
* Pedantic: This describes someone who is overly concerned with minor details and uses language in a way that is overly formal and academic.
Ultimately, the best word depends on the specific situation and your intention. You could also use a phrase like "uses a lot of big words" or "has a wide vocabulary" to describe someone who uses sophisticated language.