The Japanese just love naming things. It is ridiculous the amount of things and actions and concepts that they have exclusive names for. One prime example can be found in the katana (daito); every single piece has a name, so, to help my fellow sword enthusiasts, I've compiled this list. enjoy.
Tsuka: The hilt of the sword. The hilts of most katana are approximately 3-hand lengths. This as they are designed for two-handed use, though, as mentioned, they may be used one-handed such as in iaido (batto). Many prefer a tsuka of longer length as it can increase the amount of force produced in the slash. The length, in the end is a matter of opinion. One hand is placed at the bottom, near the kashira; the other is placed at the top, just under the tsuba.
Mekugi: These are the pegs running through the tsuka that attach it to the nakago. They usually number two or three.
Mekugi ana: The holes the mekugi are run through.
Tsuba: This is the piece traditionally referred to as the hand guard. I fear this is a misnomer as the tsuba is not intended to prevent an opponent's sword from severing your hand. It is, instead, designed to keep your inept self from inadvertently sliding your hand up onto the blade. The tsuba is often intricately decorated and is, itself a work of art.
Seppa: Spacer between the tsuka and the tsuba, and between the tsuba and the blade. Keeps the Tsuba in place.
Kashira: The endcap on the tsuka. Keeps the tsuka-ito bound.
Fuchi: A fitting between the tsuka and tsuba. (also fuchi gana)
Same: This is the ray skin with which the tsuka is wrapped (not the tsuka-ito).
Tsuka-ito: Cord that is wrapped around the tsuka. It increases gripping ability and is pretty. Though There are many ways it can be wrapped, the method most commonly used is called the tsuka maki . This method produces the diamond pattern seen on most katana tsuka
Menuki: A small ornament placed under the tsuka-ito. This is obviously not an integral part of the sword, and is often not found in swords meant for business.
Ha: The sharpened edge of the blade. The ha is often composed of a harder steel than the mune, and I have heard a number of different opinions on whether this is a Good Thing. Some claim that the increased hardness allows it to keep a sharper edge, while the softer jacket provides shock-absorbant qualities. Others feel that this format makes for shoddier blades.
Ha-Machi: A small notch at the base of the ha marking the end of the nakago and the beginning of the blade proper. The tsuba sits above the Ha-Machi.
Mune: The concave and unsharpened edge of the blade. When the sword is worn, the mune sits facing down, so that the ha does not bear down on the wood of the saya.
This is all I have time for right now. Expect updates.