A function 
which may (but does not necessarily) associate a given member
of the range of 
with more than one member of the domain
of 
. For example, trigonometric
functions such as 
are many-to-one since 
.
Many-to-One
See also
Domain, Multivalued Function, One-to-One, RangeExplore with Wolfram|Alpha
Cite this as:
Weisstein, Eric W. "Many-to-One." From MathWorld--A Wolfram Web Resource. https://mathworld.wolfram.com/Many-to-One.html