Each Cartan matrix determines a unique semisimple complex Lie algebra via the Chevalley-Serre, sometimes called simply the "Serre
 relations." That is, if  is a 
 Cartan matrix then,
 up to isomorphism, there exists a unique semisimple complex Lie algebra 
 (whose Cartan matrix is equivalent
 to 
)
 such that 
 is defined by a set of 
 generators 
 subject to the following Chevalley-Serre
 relations: 
1. 
 
2. 
 and 
 if 
 
3. 
 
4. 
 
5. 
 
6. .
 
Moreover, 
 has rank 
 and the 
's
 generate a Cartan subalgebra. For proof, see Serre (1987).