A sickle is a curved cutting tool used in agriculture for harvesting grain crops. It is a hand tool and was used before machines for harvesting. It has a curved blade with an attached handle. The inside part of the curve is sharp, so the user can swing the blade against the crop's base (stem or stalk), catching it in the curve and slicing it. Some sickles have a serrated (toothed) blade like a saw.
A sickle is sometimes used as a weapon. In Greek mythology, Cronus and Perseus did this.
A sickle and a hammer are the symbols of the Soviet Union and Communism. The sickle symbolizes the farmers and the hammer symbolizes the workers in factories.