Gri is a language for scientific graphics programming. The word "language" is important: Gri is command-driven, not point/click.
Some users liken Gri to LaTeX, since both provide extensive power in exchange for patience in learning syntax.
Gri can make x-y graphs, contour graphs, and image graphs, in PostScript and (someday) SVG formats. Control is provided over all aspects of drawing, e.g. line widths, colors, and fonts. A TeX-like syntax provides common mathematical symbols.
People often start using Gri by writing something like the following,
which produces an auto-scaled graph.
open file.dat read columns x y draw curve
As they learn that everything is controllable in Gri, users often start to produce complicated and specialized graphs. For example, every graph and table in this report was produced with Gri. Writing complicated code is made easier by the Gri emacs mode, which provides syntax colouring, command completion, and tight linkage to the online manual; see the screenshots for illustration.