<title>Abstract</title>
The idea that discourse is made up of sentences has been widespread among linguists. Does this traditional discourse perspective (“sententialism”) apply to casual language in daily communication? This paper examines the validity of sententialism by focusing on a type of speech called “dependent grafted speech” in Japanese conversation. Close examinations of various words, phrases, and sentences reveal that dependent grafted speech is different from sentences on two points: (i) Generally, the lexical accent of the copula at the beginning of dependent grafted speech is a high tone; and (ii) the interaction particle at the end of dependent grafted speech is not uttered with a falling intonation unless it is proceeded by a very abrupt rising intonation (“leaping” intonation). These findings cast doubt on the status of dependent grafted speech as a sentence. Moreover, they demonstrate a new conception of discourse as a mixture of diverse constituents, including sentences, dependent grafted speech, and other utterance types.