The value $f(c)$ is a relative minimum, or local minimum, of a function if $f(c)$ is the least output of $f$ around $x=c.$ Likewise, the value $f(d)$ is a relative maximum, or local maximum, of a function if $f(d)$ is the greatest output of $f$ around $x=d.$ If the function is continuous, the function switches from increasing to decreasing at a relative maximum or from decreasing to increasing at a relative minimum. Sometimes the phrase relative extrema is used to refer to both relative maximums and relative minimums. Note that a function can have one or more relative extrema, or none at all.