An asymptote is a line or curve
that approaches a given curve arbitrarily closely, but does not touch the curve.
The graph of an exponential function of the form [tex]f(x) = b^x[/tex] is a graph which gets close to the x-axis but does not touch it.
Therefore, an exponential function of the form [tex]f(x) = b^x[/tex] has a horizontal asymptote at y = 0.
