According to one embodiment, a sensor includes a base body, a first movable structure body, and a first fixed structure body. The first movable structure body includes first movable electrodes. A direction from the base body toward the first movable electrodes is aligned with a first direction. A distance between the base body and the plurality of first movable electrodes is changeable. A direction from one of the first movable electrodes toward an other one of the first movable electrodes is aligned with a second direction crossing the first direction. The first fixed structure body includes first fixed electrodes. One of the first fixed electrodes is between the one of the first movable electrodes and the other one of the first movable electrodes. A first movable electrode length along the first direction is shorter than a first fixed electrode length along the first direction.