Traditionally we had boiling and roasting chickens. I haven't seen a boiling chicken for years, I expect they used to be old stringy things but they don't bother selling them any more (except to chicken soup manufacturers).

yes, it hard to find an old soup chicken any more this side of the pond too. broilers are small chickens, that are broiled (rather than roast) they have to be somewhat small to cook through before the outsides get burnt. a half chicken is a serving for a broiler, (sometimes a quarter). Julia Child in one of her cook books details sizes of fowl, from cornish game hens (not from cornwall, i suspect) to soup hens. I think she used the USDA (dept of agraculture) but i checked there site and couldn't find the info. broilers are usually (at least in NY) about 1 kilo, to less than 1.5 kilos (2.25 to 3.25 lbs) roasters are 2 or more kilos.