x to indicate expected or average value. Called bra in quantum mechanics. Used in the form
x,y to indicate various forms of inner product. Used in the form
x,y, ... to denote an ordered set of objects. Not the same as \[RawLess]. Extensible character; grows by default to limited size. See The Mathematica Book:
\[LeftAngleBracket]
<
is by default interpreted as AngleBracket[
to indicate expected or average value. 
to indicate various forms of inner product. 
to denote an ordered set of objects. 
