From the ordinance
Density means the allowable number of dwelling units per acre. The types of density are: (a) Net density. The number of dwelling units per acre devoted to residential buildings and accessory uses within the site, but excluding land for public streets, parking, parks and playgrounds and other nonresidential uses. (b) Gross density. Computed on the basis of gross land area, including area devoted to streets and other nonresidential use, plus one-half of bounding streets and one-quarter of bounding street intersections.