What is the term for speech that is delivered spontaneously, without preparation?

The term for speech that is delivered spontaneously, without preparation, is impromptu speech. This type of speech is characterized by its immediacy and the speaker's ability to think on their feet, presenting their ideas and arguments with little to no prior planning. Impromptu speeches often occur in situations like classroom discussions, debates, or spontaneous public speaking opportunities, where the speaker must quickly organize their thoughts and communicate effectively without the luxury of rehearsal.

In contrast, formal speech refers to a planned and structured presentation often accompanied by specific protocols or standards. An extemporaneous speech, while still allowing some flexibility, is typically prepared in advance and may include notes, offering a more organized and rehearsed delivery than an impromptu speech. Finally, a memorized speech is one that is completely committed to memory before delivery, lacking the spontaneous element that defines an impromptu speech. Each of these alternatives emphasizes different levels of preparation and structure, highlighting why impromptu is distinctly recognized for its spontaneous nature.