Ninjutsu (忍術, Literally meaning: Ninja Techniques) is one of the three Core Jutsu Categories, utilizing Chakra to physically effect the world around the user.
Use of all Ninjutsu requires the use of Chakra and Hand Seal's, though it is not uncommon to see Ninjutsu without the use of said hand seals. Most Ninjutsu use of precise mixture of Shape Manipulation and Nature Transformation: Shape Manipulation is used for controlling the techniques form and movement, while Nature Transformation is used to generate and keep control of the properties that make up the technique. Both are important for the utilization of Ninjutsu, though both are not always needed.
Ninjutsu has several known Secondary Jutsu Categories: Medical Ninjutsu, Space–Time Ninjutsu, Clone Ninjutsu, Collaboration Techniques. Nintaijutsu and Ningenjutsu are special Secondary Jutsu Categories that combine Ninjutsu with the other Core Jutsu Categories of Taijutsu and Genjutsu respectively.