Although much has been written about the differences between written and conversational discourses, less work has been done on how these two discourse types differ in terms of chunking patterns. This study investigates the different meanings and chunking patterns two words have in Mandarin written and conversational discourses. To overcome the problem of comparability between written and conversational corpora, instead of using a single word, this study uses two near-synonymous Mandarin words, zhihou and yihou, both of which mean roughly ‘after’ or ‘later,’ and compare their meaning and chunking patterns in written and spoken corpora. The investigation regarding semantic distinctions revealed that in both writing and conversation, zhihou favors past and yihou favors future, and that in writing but not in conversation zhihou is more often used with immediate high transitivity actions and causal relations, whereas yihou is more often used with low transitivity states. Regarding chunking patterns, whereas conversation preserves different stages of chunking, written discourse mainly has the final clear-cut stage. This study demonstrates the importance of grounding grammatical investigations on discourse types and of the possible usefulness of using near-synonymous words or grammatical constructions as a way of getting round the problem of comparability.