Grout is a thick paste made from cement, water, and sometimes sand that fills the narrow gaps between tiles. If you look closely at a tiled bathroom floor or kitchen backsplash, those thin lines between the tiles are grout. Without it, tiles would shift around, water could seep underneath them, and the whole surface could fall apart.

When someone installs tile, they stick each piece down with adhesive, leaving small, even spaces between them. Then they spread grout across the surface, pressing it into all those gaps. Once it dries and hardens, the grout locks everything in place and creates a sealed, finished surface.

Grout usually comes in colors like white, gray, or beige, though it can be tinted to match or contrast with the tiles. Over time, grout can get stained or cracked, which is why people sometimes need to clean it with special brushes or regrout their tiles by removing old grout and applying fresh material. The word can also be used as a verb: a worker might spend an afternoon grouting the tiles in a new shower.