torus

Etymology

Borrowed from Latin torus (“a round, swelling, elevation, protuberance”).

noun

1. (geometry) The standard representation of such a space in 3-dimensional Euclidean space: a surface or solid formed by rotating a closed curve, especially a circle, about a line which lies in the same plane but does not intersect it (e.g. like a ring doughnut).
   1. (topology) A topological space which is a product of two circles.
      A 4-variable Karnaugh map can be thought of, topologically, as being a torus.
      1. {{lb|en|topology|in combination|n-torus|4-torus|etc.}} The product of the specified number of circles.
   2. A ring-shaped object, especially a large ring-shaped chamber used in physical research.
2. (architecture) A large convex molding, typically semicircular in cross section, which commonly projects at the base of a column and above the plinth.
3. (anatomy) A rounded ridge of bone or muscle, especially one on the occipital bone.
4. (botany) The end of the peduncle or flower stalk to which the floral parts (or in the Asteraceae, the florets of a flower head) are attached.
5. (botany) The thickening of a membrane closing a wood-cell pit (as of gymnosperm tracheids) having the secondary cell wall arched over the pit cavity.