Any bladed weapon which is held in one or two hands, but is not a staff or pole weapon. Use this tag when talking about martial arts which specifically focus on swords, or when swords are the main focus of the question.
A sword is any bladed weapon which is held in one or two hands, but is not a staff or pole weapon. Swords can have one or two edges, and may specialize in thrusting or slicing. Swords are generally considered larger than knives, and have the distinction of a primarily martial purpose as a side arm or main weapon. It should be noted that the difference between a sword and a knife is poorly defined; there are no generally accepted rules for when knives should be considered swords. (For instance, the german Grossmessser is often considered a sword whose name specifically means "Big/Great Knife.")
It should be noted that swords come in many varieties, and can often bear different names depending on who is talking about it. For instance, a two-handed European sword could be called Greatsword, Zweihander, Spadone, or Claymore; this is due simply to different languages and regions called the same or very similar weapons the same thing. To this end, some scholars and martial artists have developed typologies for swords, perhaps the most famous of which is Oakeshott's Typology, which specifically describes swords from Europe from 11-15 centuries. While none of this is needed to ask a question, seeking out the appropriate typology for swords of interest may be helpful.
Use this tag when talking about martial arts which specifically focus on swords, or when swords are the main focus of the question.