Gill spacing can be a useful character in determining a mushroom's identity, but it does have the drawback that we don't have a term for "normal", or "average".
The gill spacing shown here, for instance, is probably the most usual that you will see (also in store-bought mushrooms, for example); it is considered crowded, or close.
Subdistantgills are not quite distant, but not close either. Some people use the word close for this sort of gill spacing.
Once your gills get subdistant or farther apart, it's common to find partial gills, or lamellulae. Partial gills are those that only reach part of the way from the cap to the stem. They are usually present in one of two ratios. In the Hygrophorus picture, we have a 4:1 ration: between each full gill, there is a partial gill that reaches about half way to the stalk, with two tiny partial gills on either side of it. Some fungi have a 2:1 ratio, where there is only one partial gill between each full gill.
Of course, none of this has really been standardized. " Close", in particular, has been used in different publications to mean what I call crowded, what I call subdistant, or to mean something in between. While it has an "obvious" natural meaning, I try not to use it (it may slip out a few times during the course of the web site), as I find it just ambiguous, unless specially defined: for example, Lincoff(1987) gives explicit pictures of only three states: crowded, close, and distant. He may very well have the right idea.
