torus

IPA/ˈtɔː.rəs/
IPA/ˈtɔːr.əs/

torus — noun

  • torussingular
  • torusesplural

1. In mathematics, a surface shaped like a ring or a doughnut — formed by spinning

1.nounC1
Definition

In mathematics, a surface shaped like a ring or a doughnut — formed by spinning a circle around a line that lies outside the circle, so that the result is a tube with a hole through its centre.

Example

Tomás drew a torus in class by rotating a circle around a larger one.

geometry context — torus as a 3D shape

A bagel is a familiar torus — a ring with a hole through the middle.

real-world comparison: food shaped like a torus

Common collocations
  • surface of a torus
  • solid torus
  • shape of a torus
  • torus knot
  • torus model
Synonyms
  • doughnut

    Everyday comparison word, not a mathematical term — fine for informal explanation.

  • ring

    Describes any circular band — less precise than 'torus' because 'ring' can be flat (2D), while a torus is always a 3D tube.

Grammar Patterns

a torus

the torus

plural: tori or toruses

Usage Note

The plural can be either 'tori' (formal, academic) or 'toruses' (less common). In topology, 'torus' also refers to the entire solid shape (the 'solid torus').

2. In architecture, a thick, rounded ridge that wraps around the bottom part of a s

2.nounC2
Definition

In architecture, a thick, rounded ridge that wraps around the bottom part of a stone column, sitting just above the flat square base piece (called the plinth).

Example

The ancient Greek column had a wide torus at its base, just above the plinth.

architecture context — torus at column base above plinth

Hoa pointed out the torus molding on a stone pillar at the old courthouse entrance.

Common collocations
  • torus molding
  • base of a column
  • above the plinth
  • convex profile
  • stone torus
Synonyms
  • convex molding

    Describes the shape category — all torus moldings are convex, but not all convex moldings are tori.

Grammar Patterns

a torus

the torus

torus molding

Usage Note

A torus is a convex (outward-curving) molding. It is typically the lowest molding in a classical column base. Do not confuse it with a 'scotia', which is a concave (inward-curving) molding also found in column bases.

3. In anatomy, a smooth, rounded bulge on a person's bone — for example, a hard rid

3.nounC2
Definition

In anatomy, a smooth, rounded bulge on a person's bone — for example, a hard ridge that some people have on the roof of their mouth or on the inner side of their lower jaw.

Example

The dentist noticed a small torus on the roof of the patient's mouth.

dental/medical context — torus on palate

Amelia's X-ray showed a smooth torus on her lower jaw near the premolar teeth.

Common collocations
  • torus palatinus
  • torus mandibularis
  • bony torus
  • smooth torus
  • torus on the palate
Synonyms
  • protuberance

    More general medical term for any bump on a bone; 'torus' specifically describes a smooth, rounded type.

  • bony ridge

    Describes the elongated shape when the torus runs along a bone instead of being a single bump.

Grammar Patterns

a torus

torus on [body part]

plural: tori

Usage Note

The most common anatomical tori are the torus palatinus (on the roof of the mouth) and the torus mandibularis (on the inner side of the lower jaw). These growths are benign and usually symptomless.

Word family

  • toroidal
    adjectiveC2
  • toroid
    nounC2
  • tori
    nounC2

Synonym discussion

Sense: noun/1

Torus, doughnut, ring, and annulus all describe round shapes, but they differ in precision and dimension. 'Torus' is the exact mathematical term for a 3D surface shaped like a ring with a circular cross-section. In everyday language most people call this shape a 'doughnut' — fine for casual talk but too vague for technical use. A 'ring' describes any circular band and can be flat or thick, so it covers a much broader range of shapes. An 'annulus' is specifically the flat, 2D area between two concentric circles — like a metal washer or a flat ring on a table. Use 'torus' in mathematics, engineering, and 3D computer graphics. Use 'doughnut' only in informal comparisons. Use 'ring' for any loop-like object whose geometry is not precisely defined. Use 'annulus' exclusively for the 2D planar shape.

torus ↗doughnut ↗ring ↗annulus

Etymology

LatinEnglish

The word 'torus' comes directly from Latin, where it meant 'a bulge, a swelling, or a round seat or cushion'. In ancient Rome, a 'torus' was also the name for the decorative padding on couches and beds, which naturally had a rounded, bulging shape. The architectural sense — a thick rounded molding at the base of a column — was the first to enter English in the 1500s, borrowed from the Latin architectural term. Mathematicians later adopted the same word in the 1600s for the doughnut-shaped surface, because its rounded, bulging form resembled the original Latin cushion. The anatomical sense followed in the 1800s, also drawing on the idea of a smooth, rounded swelling on a bone. All three modern meanings therefore share the same core image: something that bulges outward in a smooth, rounded way.

First known use

1563

1563, in the meaning defined at sense 1