Sod is a thick mat of grass and the soil held together by its roots, cut into rectangular pieces that can be laid down to create an instant lawn. Instead of planting grass seeds and waiting weeks for them to grow, landscapers can roll out sod like a carpet and have a green lawn ready in a day. The grass is already mature and growing, with roots that quickly dig into the soil beneath.

When someone needs to repair a bare patch in their yard or landscape a new home, they might buy sod from a farm where grass is specially grown for this purpose. Workers cut it into strips or squares, roll it up, and transport it. Once laid down and watered regularly, the sod's roots grow into the ground below, making it permanent.

In British English, sod is also an old-fashioned word for earth or ground itself, which is why you might hear someone talk about “the old sod” when referring to their homeland.