ZazenZen sitting meditation, the core of zen practice, is called zazen in Japanese (坐禅; Chinese tso-chan [Wade-Giles] or zuochan [Pinyin]). During zazen, practitioners usually assume a sitting position such as the lotus, half-lotus, Burmese, or seiza postures. Awareness is directed towards one's posture and breathing. Often, a square or round cushion (zafu, 座蒲) placed on a padded mat (zabuton, 座布団) is used to sit on; in some cases, a chair may be used. In Rinzai Zen, practitioners typically sit facing the center of the room; while Soto practitioners traditionally sit facing a wall.
In Soto Zen, shikantaza meditation ("just-sitting", 只管打坐) that is, a meditation with no objects, anchors, or content, is the primary form of practice. Considerable textual, philosophical, and phenomenological justification of this practice can be found in Dogen's Shobogenzo. Rinzai Zen, instead, emphasizes attention to the breath and koan practice (q.v.).
The amount of time spent daily in zazen by practitioners varies. Dogen recommends that five minutes or more daily is beneficial for householders. The key is daily regularity, as Zen teaches that the ego will naturally resist, and the discipline of regularity is essential. Practicing Zen monks may perform four to six periods of zazen during a normal day, with each period lasting 30 to 40 minutes. Normally, a monastery will hold a monthly retreat period (sesshin), lasting between one and seven days. During this time, zazen is practiced more intensively: monks may spend four to eight hours in meditation each day, sometimes supplemented by further rounds of zazen late at night.
Dogen's teacher Rujing was said to sleep fewer than four hours each night, spending the balance in zazen.
Meditation as a practice can be applied to any posture. Walking meditation is called kinhin. Successive periods of zazen are usually interleaved with brief periods of walking meditation to relieve the legs.