Geometry (X11)
The string of the form 80x24+10+10 that every X program since the 1980s has understood as "this big, and there", with a small grammar of its own for negative numbers.
The format is WIDTHxHEIGHT followed by ±X±Y, and every part is optional. -geometry 80x24 sets only the size, +0+0 only the position. A plus measures the distance from the left or top edge to the window's nearest edge; a minus measures from the right or bottom edge to the window's far edge, so -0+0 means top right, +0-0 bottom left and -0-0 the bottom-right corner. Minus zero is thus a valid and much-used number. For most programs the units are pixels, but for xterm and other terminals they are characters, which works because the program declares its character cell as the resize increment in WM_NORMAL_HINTS.
In Xlib, XParseGeometry parses the string and returns a bitmask saying which parts were present and which were negative; XWMGeometry then translates the signs into a gravity, so that a window given -0+0 gets NorthEastGravity and stays in its corner once the window manager wraps a frame around it. The same call sets USPosition and USSize, which ICCCM treats as an order the window manager must obey rather than a suggestion. Xt made -geometry a standard option in every program, and xwininfo prints a window's current value in exactly this format so it can be pasted into the next launch. The syntax travelled well beyond X: ImageMagick's -resize 100x100 and -crop 10x10+5+5 are the same grammar. Wayland dropped the whole position half, since a toplevel there is no longer told where it is.