The verb "plan" denotes several things,
two of which interest us here. One is making
a map of a horizontal surface, such as
the ground or the floor of a building; the
other is deciding how things should go
together. These two meanings come
directly from two Latin words from which
"plan" is derived: plantare, meaning to fix
in place, and planum, meaning level
ground.
Architects tend to use "plan" in the
specific sense of a floor map, while the
average home owner tends to refer to the
more general idea of a spatial description.
In the vernacular, "drawing up the plans"
includes everything necessary to document
a house, including design, details,
sections, elevations and specifications—
the plan