Spirit is a resource used by the Monk in Diablo III.
The Spirit orb.
To defeat the inhuman evils they pit themselves against, monks draw upon inner reserves of Spirit, a resource that reflects their personal mastery and training. Normally a Monk has 150 maximum Spirit. Spirit does not normally regenerate, but many skills and items may add a slow replenishment to it. Items allow Monk to add up to +9 (+12 with Legendary items) Spirit per second and +45 (+73 with Legendary items) maximum Spirit. Inna's Mantra set adds +2 per second more. Skills also add those: Exalted Soul, for example, adds +100 maximum Spirit and +2 Spirit regeneration, Chant of Resonance gives +2 per second (when Mantras are active), The Guardian's Path increases all Spirit generation by 35%, Circular Breathing adds another +3 per second, and Kormac may increase generation by 10%. Paragon levels may grant +50 more Spirit.
In combat, it is mainly generated by primary skills aka Spirit Generators. Each attack of these skills replenishes 12-14 Spirit, with many special properties increasing that amount. Monks who chain their attacks carefully can continue a near-endless barrage of Spirit-fueled strikes, especially with supporting skills like Epiphany. Spirit Stones, Daibos, and Fist Weapons may also spawn with affixes that can either increase maximum Spirit, regenerate a Monk's Spirit reserves, or even restore their Life when they expend it.
Spirit is a valuable resource, but massive expenditures of this force allow a monk to call upon potent dodges and defensive moves, as well as monster-slaying finishing strikes. Thanks to monks' physical perfection and martial talent, they are free to deliver as many empowered strikes as their Spirit pools will allow – without waiting for ability cooldowns most of the time. Exceptionally powerful moves such as a Seven-Sided Strike, however, do need some time to recover.