StartingStepSize is an option to NDSolve and related functions that specifies the initial step size to use in trying to generate results.
f /: lhs := rhs assigns rhs to be the delayed value of lhs, and associates the assignment with the symbol f.
TargetFunctions is an option for functions such as ComplexExpand that specifies what functions to attempt to generate in the output.
TokenWords is an option for Read and related functions which gives a list of token words to be used to delimit words.
ToNumberField[a, \[Theta]] expresses the algebraic number a in the number field generated by \[Theta]. ToNumberField[{a_1, a_2, ...}, \[Theta]] expresses the a_i in the field ...
TraceDepth is an option for Trace and related functions which specifies the maximum nesting of evaluation chains that are to be included.
UnderoverscriptBoxOptions -> {opt_1 -> val_1, opt_2 -> val_2, ...} is an option for selections that specifies settings for UnderoverscriptBox objects.
VertexNormals is an option for graphics primitives which specifies the normal directions to assign to 3D vertices.
WhitespaceCharacter represents a single whitespace character in StringExpression.
WindowFloating is a notebook option that specifies whether the window for the notebook should float on top of other windows when it is displayed on the screen.