OverscriptBox[x, y] is the low-level box representation for OverscriptBox[x, y] in notebook expressions.
OverTilde[expr] displays with a tilde over expr.
OverVector[expr] displays with a right vector over expr.
Padding
(Built-in Mathematica Symbol) Padding is an option to various array and image operations that specifies what padding to use when extending beyond the original data specified.
PageFooters is an option for notebooks that specifies what should be inserted as the footer of each page of a notebook when it is printed.
PageHeaders is an option for notebooks that specifies what should be inserted as the header of each page of a notebook when it is printed.
PairedTTest[data] tests whether the mean of data is zero. PairedTTest[{data_1, data_2}] tests whether the mean of data_1\[Dash] data_2 is zero.PairedTTest[dspec, \[Mu]_0] ...
PairedZTest[data] tests whether the mean of the data is zero. PairedZTest[{data_1, data_2}] tests whether the means of data_1 and data_2 are equal.PairedZTest[dspec, ...
Pane
(Built-in Mathematica Symbol) Pane[expr] displays as a pane containing expr. Pane[expr, w] makes the pane be w printer's points wide, linewrapping the contents if necessary.Pane[expr, {w, h}] makes the ...
PaneSelector[{v_1 -> expr_1, v_2 -> expr_2, ...}, v] represents an object that displays as a pane containing the expr_i for which v_i is equal to v.