n. In heraldry, the distinction between shields made by one or more differences. See difference, n., 8.
Word Usage
"In brief, it seems that someone at Apple forgot to do the proper combo "differencing" from an OS X 10.6.0 base, so the 10. 6.3-level updates for at least some 10. 6.0-level files were accidentally left out of the initial combo package"