19.1. The name of a subfamily is a plural adjective used as a substantive; it is formed in the same manner as the name of a family (Art. 18.1) but by using the termination -oideae instead of -aceae.
19.2. Names intended as names of subfamilies, but published with their rank denoted by the term "suborder" (subordo) instead of subfamily, are treated as having been published as names of subfamilies (see also Art. 18.2).
19.3. A tribe is designated in a similar manner, with the termination -eae, and a subtribe similarly with the termination -inae.
19.4. The name of any subdivision of a family that includes the type of the adopted, legitimate name of the family to which it is assigned is to be based on the generic name equivalent to that type.
Ex. 1. The type of the family name Rosaceae Juss. is Rosa L. and hence the subfamily and tribe which include Rosa are to be called Rosoideae Endl. and Roseae DC.
Ex. 2. The type of the family name Poaceae Barnhart (nom. alt., Gramineae Juss. -- see Art. 18.5) is Poa L. and hence the subfamily and tribe which include Poa are to be called Pooideae Asch. and Poëae R. Br.
Note 1. This provision applies only to the names of those subordinate taxa that include the type of the adopted name of the family (but see Rec. 19A.2).
Ex. 3. The subfamily including the type of the family name Ericaceae Juss. (Erica L.), irrespective of priority, is to be called Ericoideae Endl., and the tribe including this type is called Ericeae D. Don. However, the correct name of the tribe including both Rhododendron L., the type of the subfamily name Rhododendroideae Endl., and Rhodora L. is Rhodoreae D. Don (1834) not Rhododendreae Brongn. (1843).
Ex. 4. The subfamily of the family Asteraceae Dumort. (nom. alt., Compositae Giseke) including Aster L., the type of the family name, is irrespective of priority to be called Asteroideae Asch., and the tribe and subtribe including Aster are to be called Astereae Cass. and Asterinae Less., respectively. However, the correct name of the tribe including both Cichorium L., the type of the subfamily name Cichorioideae W. D. J. Koch (1837), and Lactuca L. is Lactuceae Cass. (1815), not Cichorieae D. Don (1829), while that of the subtribe including both Cichorium and Hyoseris L. is Hyoseridinae Less. (1832), not Cichoriinae Sch. Bip. (1841) (unless the Cichoriaceae Juss. are accepted as a family distinct from Compositae).
19.5. A name of a subdivision of a family based on an illegitimate generic name that is not the base of a conserved family name is illegitimate. Contrary to Art. 32.1(b) such a name is validly published if it complies with the other requirements for valid publication.
Ex. 5. Caryophylloideae (Juss.) Rabeler & Bittrich, based on Caryophyllaceae Juss., nom. cons., is legitimate although it is derived from the illegitimate Caryophyllus Mill. non L.
19.6. When a name of a taxon assigned to one of the above categories has been published with an improper Latin termination, such as -eae for a subfamily or -oideae for a tribe, the termination must be changed to accord with the rule, without change of the author's name or date of publication (see Art. 32.6).
Ex. 6. The subfamily name "Climacieae" Grout (Moss Fl. N. Amer. 3: 4. 1928) is to be changed to Climacioideae with rank and author's name unchanged.
19.7. When the Papilionaceae are included in the
family Leguminosae (nom. alt., Fabaceae; see Art. 18.5)
as a subfamily, the name Papilionoideae may be used as
an alternative to Faboideae.
19A.1. When a family is changed to the rank of a subdivision of a family, or the inverse change occurs, and no legitimate name is available in the new rank, the name should be retained, and only its termination (-aceae, -oideae, -eae, -inae) altered.
Ex. 1. The subtribe Drypetinae Pax (1890) (Euphorbiaceae) when raised to the rank of tribe was named Drypeteae (Pax) Hurus. (1954); the subtribe Antidesmatinae Pax (1890) (Euphorbiaceae) when raised to the rank of subfamily was named Antidesmatoideae (Pax) Hurus. (1954).
19A.2. When a subdivision of a family is changed to another such rank, and no legitimate name is available in the new rank, its name should be based on the same generic name as the name in the former rank.
Ex. 2. Three tribes of the family Ericaceae, none
of which includes the type of that family name (Erica L.),
are Pyroleae D. Don, Monotropeae D. Don, and Vaccinieae
D. Don. The later names Pyroloideae (D. Don) A. Gray, Monotropoideae
(D. Don) A. Gray, and Vaccinioideae (D. Don) Endl. are
based on the same generic names.