Editing Spiral (section)

=== Helices {{anchor|Spiral or helix}} ===
[[File:Schraube und archimedische Spirale.png|right|thumb|An Archimedean spiral (black), a helix (green), and a conical spiral (red)]]
Two major definitions of "spiral" in the [[American Heritage Dictionary]] are:<ref name=free>"[http://www.thefreedictionary.com/spiral Spiral], ''American Heritage Dictionary of the English Language'', Houghton Mifflin Company, Fourth Edition, 2009.</ref>
# a curve on a plane that winds around a fixed center point at a continuously increasing or decreasing distance from the point.
# a three-dimensional curve that turns around an axis at a constant or continuously varying distance while moving parallel to the axis; a [[helix]].

The first definition describes a [[Plane (mathematics)|planar]] curve, that extends in both of the perpendicular directions within its plane; the groove on one side of a [[gramophone record]] closely approximates a plane spiral (and it is by the finite width and depth of the groove, but ''not'' by the wider spacing between than within tracks, that it falls short of being a perfect example); note that successive loops ''differ'' in diameter. In another example, the "center lines" of the arms of a [[spiral galaxy]] trace [[logarithmic spiral]]s.

The second definition includes two kinds of 3-dimensional relatives of spirals:
* A conical or [[volute spring]] (including the spring used to hold and make contact with the negative terminals of AA or AAA batteries in a [[Battery (electricity)|battery box]]), and the [[vortex]] that is created when water is draining in a sink is often described as a spiral, or as a [[conical helix]].
* Quite explicitly, definition 2 also includes a cylindrical coil spring and a strand of [[DNA]], both of which are fairly helical, so that "helix" is a more ''useful'' description than "spiral" for each of them. In general, "spiral" is seldom applied if successive "loops" of a curve have the same diameter.<ref name=free/>

In the side picture, the black curve at the bottom is an [[Archimedean spiral]], while the green curve is a helix. The curve shown in red is a conical spiral.

{{redirect|Space spiral|the building|Space Spiral}}

Two well-known spiral [[space curve]]s are ''conical spirals'' and ''spherical spirals'', defined below.
Another instance of space spirals is the ''toroidal spiral''.<ref name="von Seggern 1994 p. 241">{{cite book | last=von Seggern | first=D.H. | title=Practical Handbook of Curve Design and Generation | publisher=Taylor & Francis | year=1994 | isbn=978-0-8493-8916-0 | url=https://books.google.com/books?id=PVKXqob2dhAC&pg=PA241 | access-date=2022-03-03 | page=241}}</ref> A spiral wound around a helix,<ref name="Wolfram MathWorld 2002">{{cite web |date=2002-09-13 |title=Slinky -- from Wolfram MathWorld |url=https://mathworld.wolfram.com/Slinky.html |access-date=2022-03-03 |website=Wolfram MathWorld}}</ref> also known as ''double-twisted helix'',<ref name="Ugajin Ishimoto Kuroki Hirata 2001 pp. 437–451">{{cite journal | last1=Ugajin | first1=R. | last2=Ishimoto | first2=C. | last3=Kuroki | first3=Y. | last4=Hirata | first4=S. | last5=Watanabe | first5=S. | title=Statistical analysis of a multiply-twisted helix | journal=Physica A: Statistical Mechanics and Its Applications | publisher=Elsevier BV | volume=292 | issue=1–4 | year=2001 | issn=0378-4371 | doi=10.1016/s0378-4371(00)00572-0 | pages=437–451| bibcode=2001PhyA..292..437U }}</ref> represents objects such as [[coiled coil filament]]s.