diff --git a/src/math/rand/zipf.go b/src/math/rand/zipf.go
index 8db2c6f5bf..f04c814eb7 100644
--- a/src/math/rand/zipf.go
+++ b/src/math/rand/zipf.go
@@ -32,8 +32,10 @@ func (z *Zipf) hinv(x float64) float64 {
 	return math.Exp(z.oneminusQinv*math.Log(z.oneminusQ*x)) - z.v
 }
 
-// NewZipf returns a Zipf generating variates p(k) on [0, imax]
-// proportional to (v+k)**(-s) where s>1 and k>=0, and v>=1.
+// NewZipf returns a Zipf variate generator.
+// The generator generates values k ∈ [0, imax]
+// such that P(k) is proportional to (v + k) ** (-s).
+// Requirements: s > 1 and v >= 1.
 func NewZipf(r *Rand, s float64, v float64, imax uint64) *Zipf {
 	z := new(Zipf)
 	if s <= 1.0 || v < 1 {