Like the adjective, it is, in the present English, undeclined.
Generally speaking, the greater part of the cardinal numbers are undeclined.
It will be remembered that in Anglo-Saxon there was a form e, undeclined, and common to all the cases of all the numbers.
Like the adjectives, it is, in the present English, undeclined.
Generally speaking, the greater part of the numerals are undeclined, even in inflected languages.
late 14c., "to turn aside, deviate," from Old French decliner "to sink, decline, degenerate, turn aside," from Latin declinare "to lower, avoid, deviate, to bend from, inflect," from de- "from" (see de-) + clinare "to bend," from PIE *klei-n-, suffixed form of *klei- "to lean" (see lean (v.)). Sense has been altered since c.1400 by interpretation of de- as "downward." Meaning "not to consent, politely refuse," is from 1630s. Related: Declined; declining.
early 14c., "deterioration, degeneration," from Old French declin (see decline (v.)).