static SS singular_specials = litmap(
  "children", "child", "images", "image", "chess", "chess");
  
static Set<S> singular_specials2 = litset("time", "machine");

static S singular(S s) {
  if (s == null) null;
  try answer singular_specials.get(s);
  if (singular_specials2.contains(dropSuffix("s", s)))
    ret dropSuffix("s", s);
  if (s.endsWith("ness")) ret s;
  if (s.endsWith("ges")) ret dropSuffix("s", s);
  s = dropSuffix("es", s);
  s = dropSuffix("s", s);
  ret s;
}