Kata in karate is a way of transmitting information about body movement, technique and focus. The information to be learned is literally encoded in the movements, so that the body learns the principles by performing the movements correctly. Karate kata can be compared to a DNA molecule in which large amounts of information are encoded and passed on to the next generation - in this case, of students.
"Some falsely believe that mastery and progress come by knowing as many kata as possible. In the older days, one knew only about two or three at the most. Even to use one kata properly and efficiently is not an easy task. One must remember that it is quality over quantity when practicing any kata."
Wado Ryu Karate
We usually credit the development of karate in Okinawa to three main locations: Naha, Shuri and Tomari (although there were others). These three "styles" can be called Shurite, Nahate and Tomarite. Shurite and Tomarite tend toward quick linear movement, while Nahate tends toward powerful, "torqued" movement. Wado-ryu karate primarily employs kata from Shurite and Tomarite; however, Seishan, which comes from Nahate, contains some very fundamental Wado principles.
From Shurite: Pinan Kata, Naihanchi (Naifanchi), Kushanku, Passai, Jitte, Jion
From Tomarite: Chinto, Rohai, Wanshu
From Nahate and others: Seishan, Niseishi, Suparinpei
The Pinan Kata
Pinan (Pin-an) kata is studied in Wado-ryu, Shito-ryu, Shotokan and Shorin-ryu Karate. (The characters for Pinan are pronounced by their alternative sound in Shotokan karate - thus, Heian kata). There are, of course, differences between the kata from style to style. It is generally accepted that Pinan kata were developed by rearranging and breaking down more advanced kata. Originally, these kata were referred to as Chan-an or Chan-nan, but Itosu apparently renamed them at the behest of senior students to Pin-an. Shingo Ohgami suggests in his excellent book Karate Katas of Wadoryu that Otsuka returned the Heian kata to their original names of Pin-an in honor of Yasutsune Itosu, who had created them. In his own book, Otsuka suggests that a karate expert named Ing Shu Ho was probably responsible for the Pin-an kata. These five kata illustrate different principles which are summed up into Kushanku. In Wado-ryu karate the second kata (Pinan Nidan) is studied first, because of the difficulty and number of moves of Pinan Shodan. Wado teachers may also use Taikyoku (1, 2, and 3) or Shiho Kihon (four directions basic 1,2 and 3) as introduction kata for beginners.
Master Otsuka limited the basic curriculum to nine kata, which are, in order:
Pinan Nidan, Pinan Shodan, Pinan Sandan, Pinan Yondan, Pinan Godan, Kushanku, Naihanchi, (Naifanchi), Seishan, Chinto
Shingo Ohgami Sensei describes the interrelation of these kata this way
We see that the five Pinan kata sum into Kushanku, and that Naihanchi (Naifanchi) and Seishan sum with Kushanku into Chinto.
Additional kata are:
Passai, Niseishi, Wanshu, Rohai, Jitte, Jion (in some schools Suparinpei)