General:
* Speech: This is the most common and general noun for the act of speaking.
* Utterance: This refers to a single instance of speaking, a spoken word or phrase.
* Conversation: This refers to a spoken exchange between two or more people.
* Dialogue: This is a formal conversation, often between two characters in a play or story.
* Discourse: This refers to a formal and extended written or spoken communication.
More specific:
* Address: A formal speech given to an audience.
* Lecture: A formal talk on a specific subject.
* Presentation: A formal talk delivered to an audience, often with visual aids.
* Monologue: A long speech given by one person.
* Harangue: A lengthy and aggressive speech.
The best choice for you will depend on the specific context and what you want to emphasize.