Many students wonder what the difference is between aikido, jujitsu (jujutsu), judo, and aiki-jujutsu. The short answer is that all of them are "grappling" martial arts, i.e., they all deal with grabs, locks, and throws, but each emphasizes a slight different aspect of grappling. The long answer is much more complicated.
Jujutsu (also written jujitsu or jiu-jitsu) refers to Japanese hand to hand methods that existed hundreds of years ago. In samurai times, the techniques of jujutsu were used to grapple with an opponent (either with armor or without) after the warriors got too close together to use their weapons. There were many ancient family systems of jujutsu that included strikes, joint locks, throws, pins, and various armed techniques. Some systems have become extinct, but others are still practiced today, such as Hozoin Ryu, Kashima Shinden Jikishinkage Ryu, Kyoshin Meishi Ryu, and Ono Ha Itto Ryu. A well known modern descendant of Japanese jujutsu is Gracie Jujitsu, made famous in mixed martial arts fighting.
Aiki-Jujutsu refers to a form of jujutsu that emphasizes timing and strategic use of angles and circles to neutralize an attack, and control the attacker. Its movements are somewhat more circular than many of those found in the older jujutsu systems, but still include strikes, joint locks, throws, and pins. The man credited with establishing aiki-jujutsu was Takeda Sokaku, who lived from 1849 until 1943. He had a reputation as a fierce fighter, but continues to be one of the most important figures in early 20th Century martial arts development.
Aikido is a more modern offspring of jujutsu, created by a student of Takeda Sokaku named Ueshiba Morihei. Aikido emphasizes harmonizing with an opponent's attacking energy, using circular stepping and timing to apply the attacker's momentum in such a way as to overcome him or her. Aikido practitioners work hard to maintain a calm spirit and to cultivate a loving mindset. Current major schools of aikido include Aikikai, Hombu Aikido, and Yoshinkan Aikido.
Judo is a subset of jujutsu techniques selected and refined by Kano Jigoro. Originally developed as a form of physical education, judo has become one of the most popular sports in the world. In Judo, players grasp each other's uniforms and attempt to apply throws and takedowns. A full point throw wins a match. Judo concentrates on full body throws (in which the training partner falls on his back), and pins. It is one of the most physically demanding martial arts, and is very popular with children.
The Japanese Martial Arts Center in Ann Arbor, Michigan, offers instruction in Nihon Jujutsu (Japanese jujutsu) founded by Sato Shizuya, and Judo. Both are taught in a safe, systematic manner. Judo classes are available for children, as well.