下 (xià) has three common uses: as a verb meaning 'to go down, get off' (e.g., 下车 get off a car); as a classifier counting the number of times an action happens (e.g., 看一下 take a look), similar to 次 (cì) but more specific to brief, discrete actions; and as a noun meaning 'below, under' (e.g., 桌子下 under the table), which is the everyday spoken word — 下面 (xià miàn) and 底下 (dǐ xia) are more precise for 'underneath' or 'the area below'.