by wendy » Fri Jun 07, 2013 8:57 am
Shapes by dimension are given names derived from 'solid'
2d = hedrid, 3d = chorid, 4d = terid, 5d = petid, 6d = ectid, 7d = zettid, 8d = yottid.
Solid refers to covering its space. One can have an area of solid colour, where this is all of a 2d patch. But this is not a solid in 3d.
Plane figuees are by the rules of the PG, set to a space that divides all-space, since that's what a plane does.
Basically the hedrid/chorid sequence corresponds to 'dimensions', while the 'solid/plane' corresponds to 'number of equal signs to set that space. The equation "x=0" defines a line in 2d, or a hedrix in 3d, or a 3d-space in 4d, or a 4d space in 5d, is a dividing space or 'plane'. The set x=0, y=0 defines a point in 2d, a line in 3d, a 2d-space in 4d, etc, uses the general name for "two equal signs" (ie margin). A property built on a plane in N dimensions, is separated from other properties by margins. &c.