there are _voluntary_ standard published by USDA/et. al. - but note they are voluntary.
the internet has many blogs - which do not agree - some are outright wrong....
§70.201 Chickens.
The following are the various classes of chickens:
(a) Rock Cornish game hen or Cornish game hen. A Rock Cornish game hen or Cornish
game hen is a young immature chicken (usually 5 to 6 weeks of age), weighing not more than
2 pounds ready-to-cook weight, which was prepared from a Cornish chicken or the progeny of a
Cornish chicken crossed with another breed of chicken.
(b) Rock Cornish fryer, roaster, or hen. A Rock Cornish fryer, roaster, or hen is the
progeny of a cross between a purebred Cornish and a purebred Rock chicken, without regard to
the weight of the carcass involved; however, the term "fryer," "roaster," or "hen," shall apply
only if the carcasses are from birds with ages and characteristics that qualify them for such
designation under paragraphs (c) and (d) of this section.
(c) Broiler or fryer. A broiler or fryer is a young chicken (usually under 13 weeks of
age), of either sex, that is tender-meated with soft, pliable, smooth-textured skin and flexible
breastbone cartilage.
(d) Roaster or roasting chicken. A bird of this class is a young chicken (less than 12
weeks of age), of either sex, with a ready-to-cook carcass weight of 5.5 pounds or more, that
is tender-meated with soft, pliable, smooth-textured skin and breastbone cartilage that is
somewhat less flexible than that of a broiler or fryer.
(e) Capon. A capon is a surgically unsexed male chicken (usually under 8 months of
age) that is tender-meated with soft, pliable, smooth-textured skin.
(f) Hen, fowl, or baking or stewing chicken. A bird of this class is a mature female
chicken (usually more than 10 months of age) with meat less tender than that of a roaster or
roasting chicken and nonflexible breastbone tip.
(g) Cock or rooster. A cock or rooster is a mature male chicken with coarse skin,
toughened and darkened meat, and hardened breastbone tip.
