Seiza
Seiza (正座, literally "correct sitting") is a Japanese word which describes the traditional formal way of sitting in that country.To sit seiza-style, one first kneels on the floor, and then rests the buttocks on the heels, with the tops of the feet flat on the floor. The hands are usually folded modestly in the lap and the back kept straight.
Seiza is most often done on tatami (woven straw mat) floors, but many people sit seiza-style on carpeted and even hardwood floors. Depending on the formality of the occasion, the setting, and the relative status of the person, it is sometimes acceptable to sit on a special cusion called a zabuton (座布団, literally a "sitting futon").
Sitting cross-legged is considered informal and is inappropriate for certain situations, but is sometimes permitted, especially for those for whom seiza is difficult, such as elderly or non-Japanese people (though in the case of the latter it is advisable, particularly in formal situations, to at least try). Sometimes stools are provided for elderly or injured people even when others are expected to sit seiza-style.
Doing seiza is an integral and required part of several traditional Japanese arts, such as tea ceremony and certain martial arts. Seiza is also the traditional way of sitting while doing other arts such as shodo (calligraphy) and ikebana (flower arranging), though with the increasing use of western-style furniture it is not always necessary for these nowadays.