First
(Built-in Mathematica Symbol) First[expr] gives the first element in expr.
FontColor is an option for Style, Cell, and related constructs that specifies the default color in which to render text.
FrameBox[box] is a low-level box construct which represents box with a frame drawn around it.
GenerateConditions is an option for Integrate, Sum, and similar functions that specifies whether explicit conditions on parameters should be generated in the result.
HankelMatrix[n] gives the n*n Hankel matrix with first row and first column being successive integers.HankelMatrix[{c_1, c_2, ..., c_n}] gives the Hankel matrix whose first ...
HessenbergDecomposition[m] gives the Hessenberg decomposition of a matrix m.
HoldPattern[expr] is equivalent to expr for pattern matching, but maintains expr in an unevaluated form.
Identity[expr] gives expr (the identity operation).
IgnoreCase is an option for string manipulation and searching functions that specifies whether lowercase and uppercase letters should be treated as equivalent.
Infix
(Built-in Mathematica Symbol) Infix[f[e_1, e_2, ...]] prints with f[e_1, e_2, ...] given in default infix form: e_1~f~e_2~f~e_3 .... Infix[expr, h] prints with arguments separated by h: e_1 h e_2 h e_3 ...