T: 1) polynomial time transformation
2) answer preserving
eg. SAT 
K-Clique
T: 
Clique size k = k number of clauses
T: polynomial in k and n.
SAT
length O(kn logn)
time for T: kn nodes
and 
edges
total 
If 
NP-Complete (NPC)
A problem 
is NP-complete if 
and
for every other problem 
If 