noun, plural hel·i·ces [hel–uh-seez] /ˈhɛl əˌsiz/, he·lix·es.

- a spiral.
- Geometry. the curve formed by a straight line drawn on a plane when that plane is wrapped around a cylindrical surface of any kind, especially a right circular cylinder, as the curve of a screw. Equation: x = a sinθ, y = a cosθ, z = b θ.
- Architecture.
- a spiral ornament.
- (in a Corinthian capital) either of two scrolls issuing from a cauliculus.Compare Corinthian(def 2).

- Anatomy. the curved fold forming most of the rim of the external ear.
- Biochemistry. alpha helix.

noun plural helices (ˈhɛlɪˌsiːz) or helixes

- a curve that lies on a cylinder or cone, at a constant angle to the line segments making up the surface; spiral
- a spiral shape or form
- the incurving fold that forms the margin of the external ear
- another name for volute (def. 2)
- any terrestrial gastropod mollusc of the genus Helix, which includes the garden snail (H. aspersa)

“a spiral thing,” 1560s, from Latin helix “spiral,” from Greek helix (genitive helikos), related to eilein “to turn, twist, roll,” from PIE *wel-ik-, from root *wel- “to turn, revolve” (see volvox).

n. pl. he•lix•es

- A spiral form or structure.
- The folded rim of skin and cartilage around most of the outer ear.
- A three-dimensional curve that lies on a cylinder or cone, so that its angle to a plane perpendicular to the axis is constant.

- A three-dimensional spiral curve. In mathematical terms, a helix can be described as a curve turning about an axis on the surface of a cylinder or cone while rising at a constant upward angle from a base.
- Something, such as a strand of DNA, having a spiral shape.

In geometry, a three-dimensional spiral shape, resembling a spring.