az-

1.
variant of azo-, especially before a vowel:
azine.
British Dictionary definitions for az-

aza-

combining form
1.
denoting the presence of nitrogen, esp a nitrogen atom in place of a -CH group or an -NH group in place of a -CH2 group: azathioprine
Word Origin
C20: from az(o)- + -a-

azo-

combining form
1.
indicating the presence of an azo group: azobenzene
Word Origin
from French azote nitrogen, from Greek azōos lifeless, from a-1 + zōē life
az- in Science
azo- or az-  
A prefix that means "containing an azo group attached at both ends to other groups," as in the compound azobenzene.