# What is the difference between helix and spiral?

The words spiral and helix are both used for curves that "wind around". For example, both searches "DNA spiral" and "DNA helix" (with quotation marks) result in many thousands of Google hits.

Is there a difference between helix and spiral, or are these words synonyms?

[Note: I take that back about plane curves --- the tangent line to any curve in the $xy$ plane (at any point on it) is at a 90 degree angle from the $z$ axis, so that any curve in the $xy$ plane would qualify as a helix under the constant angle definition. That makes such curves not good candidates for the term ""helix", i.e. the notion is trivially true for all plane curves.]