tertiary

Plural: tertiaries

Noun

A tertiary flight feather; a tertial.
from 63 million to 2 million years ago
Any item considered to be of third order.
A tertiary colour.
Something from the Tertiary Period (the former term for the geologic period from 65 million to 2.58 million years ago).
A tertiary feather; a tertial.
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.
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.

Adjective Satellite

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

Adj

Of third rank or order; subsequent.
Possessing some quality in the third degree; especially having been subjected to the substitution of three atoms or radicals.
Of quills: growing on the innermost joint of a bird's wing; tertial.

Examples

A gigaton-scale weapon would of necessity be a three-stage design (incorporating a fusion tertiary - likely with its own massive fission tamper - in addition to the fission primary and fission-jacketed fusion secondary), as a reasonably-sized primary would likely have difficulty imploding to ignition the enormous secondary that would be required to reach a one-gigaton yield with a two-stage thermonuclear.
a tertiary alcohol, amine, or salt
The tertiary education of Scrabble players often involves memorizing obscure bird feather terms.

Origin / Etymology

PIE word
*tréyes
Borrowed from the Latin tertiārius (“of the third part or rank”), from tertius (“third”) (from Proto-Indo-European *tr̥tyós, whence English third) + -ārius (whence the English suffix -ary); compare the French tertiaire.

Synonyms

3rd, Tertiary period, third, ternary, tertial

Scrabble Score: 11

tertiary: valid Scrabble (US) TWL Word
tertiary: valid Scrabble Word in Merriam-Webster MW Dictionary
tertiary: valid Scrabble Word in International Collins CSW Dictionary

Words With Friends Score: 10

tertiary: valid Words With Friends Word