Formal:
* Monologue: This refers to a long speech by one person, often in a play or other performance.
* Address: This is a formal speech delivered to a group of people, usually on a specific occasion.
* Lecture: This is a formal talk given to a group of people on a specific topic.
* Presentation: This is a more informal term for a speech, often used in a business or academic setting.
Informal:
* Speech: This is a general term for any spoken communication, but can also refer specifically to a formal address.
* Talk: This is a more informal term for a speech, often used for less formal presentations.
* Discourse: This is a more academic term for a formal and extended speech or writing.
The best word to use will depend on the specific situation and the tone you are trying to convey.