Please note that the content of this book primarily consists of articles available from Wikipedia or other free sources online. In mathematics, an annulus (the Latin word for "little ring", with plural annuli) is a ring-shaped geometric figure, or more generally, a term used to name a ring-shaped object. Or, it is the area between two concentric circles. The adjectival form is annular (for example, an annular eclipse).

Данное издание не является оригинальным. Книга печатается по технологии принт-он-деманд после получения заказа.