Half-Dimensions

[Jay]

I heard this term used before in some other website talking about dimenionality. However, I do not understand it at all. How can an object be say, 2.5-dimensional?

[Keiji]

2.5 dimensions is used (wrongly) to refer to isometric graphics. All spaces must have a whole number of dimensions.

In other words, whoever you heard that from is wrong.

[Aale de Winkel]

fractional "dimensions" you have in figures call fractals this way:
the figure _/\_ is a line having 4 parts in the "space" of 3 parts and thus has "dimension" 3/4
this kind of dimension has nothing to do with the dimension of a space.
to distinguish one probably best call this "fractal dimension".
as a nutural example a shore-line is a sample of a line having broken "fractal dimension".

there are various "fractal generating programs" around.
the fun with fractals is that one can zoom in on some part and essentially end up with the same picture, consider pe each of the four lines above also having the same _/\_ shape etc ad infinitum.
with shorelines, snowflakes etc the same thing happens.

see http://mathworld.wolfram.com/Fractal.html for various samples.
so no-one is wrong, it is simply quite something else