Compare those 2 sentances: > "The base SL distribution is basically Enterprise Linux, recompiled from > source. -snip- > "Q. What is Scientific Linux? > > A. Scientific Linux is in essence, a commercial enterprise linux > distribution, recompiled. and compare it with this statement: "CentOS conforms fully with the upstream vendors redistribution policy and aims to be 100% binary compatible. (CentOS mainly changes packages to remove upstream vendor branding and artwork)." For me, "basically" and "in essence" is not as same as "aims to be 100% binary compatible" If you can not see and understand, then I, or anyone else, can not help you to understand the difference. Ljubomir