A knife (plural knives) is a cutting tool with a cutting edge or blade, hand-held or otherwise, with or without a handle. Knife-like tools were used at least two-and- a-half million years ago, as evidenced by the Oldowan tools.
Originally made of rock, bone, flint, and obsidian, knives have evolved in construction as technology has, with blades being made from bronze, copper, iron, steel, ceramics, and titanium. Many cultures have their unique version of the knife.
A sword is a weapon (edged weapon) used primarily for cutting or thrusting. The precise definition of the term varies with the historical epoch or the geographical region under consideration. A sword in the most narrow sense consists of a straight blade with two edges and a hilt. However, in nearly every case, the term may also be used to refer to weapons with a single edge (backsword).