A quantity that is nonzero everywhere is said to be nonvanishing. For instance, the values of 
are nonvanishing for real 
, while those of 
are not (since 
vanishes at 
).
Nonvanishing
See also
Nonzero, Vanish Identically, Vanishing, ZeroExplore with Wolfram|Alpha
Cite this as:
Weisstein, Eric W. "Nonvanishing." From MathWorld--A Wolfram Web Resource. https://mathworld.wolfram.com/Nonvanishing.html