‘以来’ (yǐ lái) is a time-related preposition meaning 'since' or 'from...onward'. It attaches to a specific point in time — such as a year, date, event, or noun phrase indicating a temporal starting point — and marks the beginning of a period that continues up to the present or another reference time. The character 以 (yǐ) means 'by', 'with', or 'using', and 来 (lái) means 'to come'; together, they convey the idea of 'coming from [that point] onward'. Unlike English 'since', ‘以来’ cannot stand alone as a sentence element — it must follow a time noun or phrase and usually appears before the main verb.

This expression is common in both spoken and written Chinese, especially in formal or narrative contexts describing ongoing situations, changes, or accumulated experiences. It often pairs with duration words like ‘一直’ (yìzhí, 'continuously') or ‘已经’ (yǐjīng, 'already'), and frequently appears in structures like ‘自从…以来’ (zìcóng…yǐ lái), though ‘以来’ alone suffices when the starting point is clear from context.