Formal:
* Seminar leader: This is the most common and neutral term.
* Instructor: This is appropriate if the seminar involves teaching a specific skill or subject.
* Facilitator: This implies that the seminar leader helps participants to learn and engage with the material, rather than simply delivering information.
* Speaker: This term is appropriate if the seminar is more of a lecture or presentation.
* Presenter: Similar to speaker, this emphasizes the presentation aspect of the seminar.
Informal:
* Teacher: This term is suitable for someone who is teaching a skill or subject.
* Trainer: This term is used for someone who is teaching practical skills.
* Coach: This term is used for someone who is providing guidance and support to participants.
* Expert: This term suggests that the seminar leader has significant knowledge and experience in the subject matter.
The best term to use depends on the specific context of the seminar.