The smallest bounded unit of a living body or a grid. A cell has a wall, which is what makes it one thing.
Latin cella (a small room, a monk's cell), related to celare (to hide, to conceal); Robert Hooke borrowed the monastic sense in 1665, comparing the small compartments he saw in cork under a microscope to a monastery's row of tiny rooms.
The smallest bounded unit of a living body, or of a grid — a cell has a wall, and the wall is what makes it one thing rather than a smear.