In this paper, I will discuss the functional aspects of parenthetical clauses and sentences in spontaneous Japanese monologues. Parentheticals can be defined as syntactic elements that are instantly inserted in the middle of an ongoing utterance to add supplemental information and thus interrupts the fluent flow of speech production. Examples of parenthetical clauses/sentences that appeared in the Corpus of Spontaneous Japanese were examined and then classified into three types. These types differ in their contextual functions, but share a commonality in that they present multiplex information simultaneously in the process of producing spontaneous speech.

Index Terms: parenthetical clause/sentence, Corpus of Spontaneous Japanese, contextual functions