1) Ancient Greek art 2) Composition in visual art 3) Two-direction section 4) Type of highway bend 5) Winding road section 
An S curve or S-curve describes a sigmoid function, a mathematical function that produces a sigmoid, or `S`-shaped, curve. S Curve or S-curve can also refer to the following: ...[art] The S Curve is a traditional art concept in Ancient Greek sculpture and Roman sculpture where the figure`s body and posture is depicted like a sinuous or serpentine `S`. It is related to and is an extension of the art term of contrapposto which is when a figure is depicted slouching or placing one`s weight and thus center of gravity t...
Two connected turns that travel in alternate directions.
: see below.