Fa jin, fajin, or fa chin (fā jìn, 發勁) is a term used in some Chinese martial arts, particularly the neijia (internal) martial arts, such as Xingyiquan, T'ai chi ch'uan (Taijiquan), Baguazhang and Bak Mei.
It means to issue or discharge power explosively, and is not specific to any particular striking method. Jìn (勁), or "power", is often confused by Westerners with the related concept of jīng (精), which literally means "essence."