Kekkei genkai (血継限界; Literally meaning "a technique limited to inheritance by blood" or "Bloodline Limit") are abilities passed down genetically within specific clans. It's possible for a beings to have more than one of these abilities. Kekkei genkai abilities that work via the user's eye are called dōjutsu. Other kekkei genkai include mixing one type of elemental chakra with another, creating a new one unique to the users, which is usually impossible for normal ninja. Kekkei genkai and their related techniques cannot be taught to or copied by others. However, kekkei genkai can be given to others. Dōjutsu, or other kekkei genkai isolated to a single organ, can be transplanted into the body of another. Use of these organs requires much more chakra than someone born with the kekkei genkai. Chakra elements can also be passed down to people outside of the clan.
Although kekkei genkai are usually genetically shared within a specific clan, sometimes it is unique to one person alone, and that even family relatives do not share it, such as the Wood Release and Shikotsumyaku. Yet other kekkei genkai seem to appear in individuals with no known relation, such as the Lava Release, which has appeared in ninja from Kirigakure, Iwagakure, and Kumogakure, while Magnet Release, which has appeared in ninja from both Kumogakure and Sunagakure.
Kekkei tōta (血継淘汰; Literally meaning "a selection of blood inheritance" or "Bloodline Selection") is an advanced and very rare form of a kekkei genkai.
Dōjutsu (瞳術; Eye Techniques) are genetic ninja abilities that utilise the eyes, granting the wielder ocular abilities. Being a by-product of specific kekkei genkai, dōjutsu are not classified as one of the major jutsu types. They do not require the use of hand seals and in some cases facilitate in the use of or defense against genjutsu, taijutsu and ninjutsu and then defeat their opponent. All known dōjutsu also provide the user with some unique abilities, such as an extended field of vision or predictive capabilities. The use of dōjutsu often-time consumes a great deal of chakra. It should also be noted that along with the eye itself, techniques that stem from the eye's use are also known as dōjutsu.
By transplanting the eye in question, it is possible for people to possess the dōjutsu, despite not being in the clan that the dōjutsu originates from. Among all known dōjutsu, the Byakugan, Rinnegan, and Sharingan are known collectively as the Three Great Dōjutsu (三大瞳術, San Daidōjutsu; Literally meaning "Three Great Eye Techniques").