Let 
be a complete normal variety, and write 
for the group of divisors, 
for the group of divisors numerically equal to 0, and
the group of divisors algebraically equal to 0. Then the finitely generated quotient
group 
is called the Néron-Severi group.
Néron-Severi Group
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References
Iyanaga, S. and Kawada, Y. (Eds.). Encyclopedic Dictionary of Mathematics. Cambridge, MA: MIT Press, p. 75, 1980.Referenced on Wolfram|Alpha
Néron-Severi GroupCite this as:
Weisstein, Eric W. "Néron-Severi Group." From MathWorld--A Wolfram Web Resource. https://mathworld.wolfram.com/Neron-SeveriGroup.html