There is a sentence in Sokal and Rohlf's classic text [R.R.Sokal F.J.Rohlf; Biometry, 3rd ed., 1994: p.132, chapter 7 Estimation and Hypothesis Testing]:
The variance of means is therefore partly a function of the sample size on which the means are based.
In this specific case, I understand that the greater the sample size the lesser the standard deviation of sample means. But in general what does it mean to be a function of something? Relationship or dependence?
(Please provide answers/comments in plain language.)