长度 (cháng dù) is a noun meaning 'length'—the measurement of how long something is from end to end. It combines 长 (cháng), meaning 'long', and 度 (dù), meaning 'measure' or 'degree'; together, they literally mean 'measure of length'. This word is used in both everyday and technical contexts—for example, when describing the size of an object, calculating distances, or specifying dimensions in construction, sewing, or science.

Unlike the verb form of 长 (zhǎng, 'to grow'), here 长 is pronounced cháng and functions strictly as part of a compound noun. 长度 is always used with measure words (e.g., 米 for meters) or quantifiers (e.g., 这个长度, 多长的长度), and it never stands alone as a standalone measurement—it must be paired with a number or descriptive phrase. It’s neutral in register and common across spoken and written Chinese.