Kamui

By focusing his Mangekyō Sharingan on a particular point within a barrier this technique creates, Kakashi can force that point to collapse in on itself, ultimately sending everything in the vicinity to another dimension. Kamui costs a large amount of chakra to perform, especially in Kakashi's case, as his non-Uchiha body is not compatible with the eye, meaning it may cause Kakashi more strain or fatigue than an actual Uchiha using the technique. Kakashi has only been shown to use this technique up to three times in a given day, even when starting at full strength. When first seen, Kakashi's aim and control over the size of the barrier was imperfect. It took him two attempts to hit Deidara with the technique (still not being able to successfully take Deidara's head). Additionally, after he warped away an explosion made by Deidara, the point continued to collapse on itself even after he had transported the explosion. By the time of Pain's attack on Konoha, however, his aim improved, being able to focus more accurately on fast-moving objects. He was even able to control the barrier size effectively enough that Pain did not notice that he warped away the nail he sent flying at him, suggesting that he did not make the barrier any larger than necessary to transport the nail to another dimension. This is significant, since the chakra used by this technique is proportional to the mass of the target transported. His improvement with the technique is also seen when he manages to warp away two arrows fired by Sasuke's Susanoo (that he noted to be too fast to dodge) without immediately becoming fatigued.

Influence
Kamui is the word for a divine being in Ainu mythology, although it is almost never written with kanji in modern times. In a more general Japanese context, Kamui refers to the might and majesty of the gods, particularly the Shintō Kami.

Trivia

 * Kakashi's Kamui bears some resemblance to Madara Uchiha's space time technique as Madara's appearance when he is warping between different dimensions is just like the appearance of Kamui. It is unknown if the two techniques are related, however.
 * According to the Third Databook, "If one spends a lot of time and trains one's chakra over and over again, this technique can be invoked." This might hint that other Mangekyō users can access the technique, but this is not confirmed.