Answer:
Informal speech is more casual and spontaneous, while formal speech is more professional.
Step-by-step explanation:
Informal speech often includes slangs, contractions, colloquial language, etc. For instance, informal speech would be like the type of language you use when having a casual conversation with a friend.
Formal speech doesn't often include slangs, contractions, colloquial language, etc. Formal speech is usually used for professional or academic purposes.