Ancillary vs. Tertiary — What's the Difference?

Of secondary importance; subordinate

Tertiary ( TUR-shə-ree, TUR-shee-err-ee) is a widely used but obsolete term for the geologic period from 66 million to 2.6 million years ago. The period began with the demise of the non-avian dinosaurs in the Cretaceous–Paleogene extinction event, at the start of the Cenozoic Era, and extended to the beginning of the Quaternary glaciation at the end of the Pliocene Epoch.

Auxiliary or accessory

Third in place, order, degree, or rank.

Something that is subordinate or accessory to something else

Of, relating to, or designating the short flight feathers nearest the body on the rear edge of a bird's wing.

A person working in a supportive or subordinate role

Of, relating to, or having a carbon atom that is attached to three other carbon atoms in a molecule.

Subordinate; secondary; auxiliary.

Of or relating to the replacement of three of several atoms or groups in a compound, such as an amine in which three valences of the functional group are taken by carbon atoms.

Something that serves an ancillary function, such as an easel for a painter.

Of or relating to salts of acids containing three replaceable hydrogen atoms.

(archaic) An auxiliary.

Tertiary Of, relating to, or being the period of geologic time from about 66 to about 2.6 million years ago, the older of the two periods of the Cenozoic Era. The Tertiary Period is characterized by the appearance of modern flora, insects, fish, amphibians, and reptiles, and by the dominance of mammals as vertebrate life forms on land. See Table at geologic time.

Subservient or subordinate, like a handmaid; auxiliary.

A tertiary feather.

Relating to something that is added but is not essential;

Tertiary The Tertiary Period.

Roman Catholic Church A member of a religious Third Order.

Of third rank or order; subsequent.

(chemistry) Possessing some quality in the third degree; especially having been subjected to the substitution of three atoms or radicals.

(ornithology) Of quills: growing on the innermost joint of a bird's wing; tertial.

Any item considered to be of third order.

A tertiary colour.

(geology) Something from the Tertiary Period (the former term for the geologic period from 65 million to 2.58 million years ago).

(ornithology) A tertiary feather; a tertial.

(military) A large stage in some extremely powerful thermonuclear weapons (resembling a greatly-enlarged secondary) which is compressed by the explosion of the secondary until ignition of nuclear fusion takes place, in much the same manner as the secondary is imploded by the primary, and which can allow for the attainment of yields of many tens or even hundreds of megatons, and likely even greater; not used in modern weapons due to a greater focus on the accurate use of sub-megaton weapons, the tremendous size of weapons incorporating a tertiary, and the lack of targets whose destruction would necessitate the use of a three-stage weapon.

(Roman Catholicism) A member of a Roman Catholic third order; a layperson who participates in activities similar to those engaged in by men and women who take religious vows (respectively the first and second orders), and who may wear some elements of an order's habit such as a scapular.

Being of the third formation, order, or rank; third; as, a tertiary use of a word.

Possessing some quality in the third degree; having been subjected to the substitution of three atoms or radicals; as, a tertiary alcohol, amine, or salt. Cf. Primary, and Secondary.

Later than, or subsequent to, the Secondary.

Growing on the innermost joint of a bird's wing; tertial; - said of quills.

A member of the Third Order in any monastic system; as, the Franciscan tertiaries; the Dominican tertiaries; the Carmelite tertiaries. See Third Order, under Third.

The Tertiary era, period, or formation.

One of the quill feathers which are borne upon the basal joint of the wing of a bird. See Illust. of Bird.

From 63 million to 2 million years ago

Coming next after the second and just before the fourth in position