Japanese word «yari» (spear) describes a wide variety of polearms designed for different combat situations. The spear with a straight two-edged blade was called su yari. Two other types of spears with a straight blade were called sankaku yari and ryo-shinogi yari. Their blades were triangular (sankaku yari) and diamond-shaped ( ryo-shinogi yari). The last type of straight-bladed yari was omi yari – a spear with a very large blade (in other respects it was similar to su yari). Other spears had a blade of more complex form. The Jumonji yari, for example, had three blades – the central was straight while the other ones perpendicular to the central blade were curved. Kata kama yari, on the other hand, had two blades, both straight – the central blade was crossed by the other one, usually assymetrically, so that the length of the other blade on one side of the main blade exceeded its length on the other side. The most unusual type of spear was tsuki nari yari – it had a crescent-shaped blade.
The spears were classified not only by shape of their blades, but also by the length of their poles. The longest ones were called nagae yari, their length ranged from 4.5 to 6.5 meters. Such spears (they are actually more pikes then spears) were used only by ashigaru in dense formations. Shorter spears were called mochi yari. Other, even shorter spears, called makura yari, were used in confined conditions, for example, inside buildings.
Although spears existed in Japan since ancient times, they became widespread relatiwely late- during the XIV century. Before that time, the most popular polearm in Japan was naginata, which can be easily recognized by its long and slightly curved blade. Naginata was most popular amongst sohei, the Japanese warrior-monks. During the Sengoku period naginata was still a widely used weapon, although it lost its position of main weapon of infantry to yari. Also, naginata was one of those weapons which samurai women were trained to use. When in the Edo period major conflicts ceased and naginata fell into relative disuse, it became a symbol of samurai-class woman, and was considered as chiefly a woman’s weapon since.
Taken from the original website by ZVEZDA.
http://samurai-battles.com/historical-reference/japanese-spears-and-polearms/