Formal:
* Address: This is a formal, prepared speech given to a group of people.
* Lecture: A formal talk on a specific topic, often given in an educational setting.
* Presentation: A structured talk, often using visual aids, to convey information.
* Keynote address: A major speech delivered at a conference or event, often setting the tone for the event.
* Oration: A formal, eloquent speech, often delivered on a special occasion.
Informal:
* Talk: A general term for any spoken presentation to an audience.
* Speech: A general term for any formal or informal presentation.
* Presentation: A more casual term than "address" or "lecture," often used for informal talks.
The best term to use will depend on the specific context of the speech. For example, a speech given at a graduation ceremony might be called an "address" or "oration," while a speech given at a business meeting might be called a "presentation" or "talk."