Throughout this document an attempt has been made to maintain consistency of
nomenclature. This cannot be wholly successful because as gnuplot has
evolved over time, certain command and keyword names have been adopted that
preclude such perfection. This section contains explanations of the way
some of these terms are used.
A "page" or "screen" is the entire area addressable by gnuplot. On a
monitor, it is the full screen; on a plotter, it is a single sheet of paper.
A screen may contain one or more "plots". A plot is defined by an abscissa and an ordinate, although these need not actually appear on it, as well as the margins and any text written therein.
A plot contains one "graph". A graph is defined by an abscissa and an ordinate, although these need not actually appear on it.
A graph may contain one or more "lines". A line is a single function or data set. "Line" is also a plotting style. The word will also be used in sense "a line of text". Presumably the context will remove any ambiguity.
The lines on a graph may have individual names. These may be listed together with a sample of the plotting style used to represent them in the "key", sometimes also called the "legend".
The word "title" occurs with multiple meanings in gnuplot. In this
document, it will always be preceded by the adjective "plot", "line", or
"key" to differentiate among them.
A graph may have up to four labelled axes. Various commands have the name of
an axis built into their names, such as set xlabel. Other commands have
one or more axis names as options, such as set logscale xy. The names of
the four axes for these usages are "x" for the axis along the bottom border
of the plot, "y" for the left border, "x2" for the top border, and "y2" for
the right border. "z" also occurs in commands used with 3-d plotting.
When discussing data files, the term "record" will be resurrected and used to denote a single line of text in the file, that is, the characters between newline or end-of-record characters. A "point" is the datum extracted from a single record. A "datablock" is a set of points from consecutive records, delimited by blank records. A line, when referred to in the context of a data file, is a subset of a datablock.