Pumping Lemma

Teacher briefly mentioned this in MATH239 for proving that something is a Context-Free Language. Would see in CS360.

http://www2.lawrence.edu/fast/GREGGJ/CMSC515/chapt01/Pumping.html

If A is a regular language, then there is a number p where if s is any string in A of length at least p, then s may be divided into three pieces, s = xyz, satisfying the following conditions:

1. for each $i\ge 0,x{y}^{i}z\in A$
2. $|y|>0$, and
3. $|xy|\le p$