FontSize is an option for Style and Cell that specifies the default size in printer's points of the font in which to render text.
GeodesicDilation[marker, mask] gives the fixed point of the geodesic dilation of the image marker constrained by the image mask.
Gudermannian[z] gives the Gudermannian function gd(z).
ImageDifference[image_1, image_2] gives an image in which each pixel is the absolute difference of the corresponding pixels in image_1 and image_2.
ImageSubtract[image, x] subtracts a constant amount x from each channel value in image.ImageSubtract[image_1, image_2] gives an image in which each pixel is obtained by ...
LaplacianFilter[image, r] convolves image with a range r Laplacian kernel.LaplacianFilter[image, {r_1, r_2}] uses ranges r_i in the vertical and horizontal ...
MaxFilter[image, r] filters image by replacing every value by the maximum in its range r neighborhood. MaxFilter[data, r] applies max filtering to an array of data.
Rationals represents the domain of rational numbers, as in x \[Element] Rationals.
RiemannR[x] gives the Riemann prime counting function R(x).
SetFileDate["file"] sets the modification and access dates for a file to be the current date.