This study provides a definition of the genre of conversation by describing nine features of conversation, namely multiple sources, discourse coherence, language as doing, co-operation, unfolding, open-endedness, artifacts, inexplicitness and shared responsibility. These nine features of naturalness in conversation serve to distinguish conversation from specialized discourse types. The study illustrates the nine defining features of conversation with authentic conversational data collected surreptitiously in England. While this study is of native speakers of English, the nine defining features of naturalness of English conversation are applicable to conversations conducted in other languages.