Other forms: invalids
A ticket is invalid when it will not get you through the gate: out of date, wrong name, missing a stamp. An argument is invalid when the conclusion does not follow from what came before it.
Invalid is what forms and computers say when something will not do — invalid password, invalid date, invalid entry — and it is the plain opposite of valid, so a contract can be invalid, a vote can be invalid, and a passport goes invalid the day it expires. Then there is the trap, and it is worth ten minutes of your attention. Spelled the same but stressed differently, an invalid is a person too ill to look after themselves: in-VAL-id for the ticket, IN-va-lid for the person. That second word is dated and unkind, and you should leave it where you found it. The verb is invalidate — one missing signature invalidates the whole form.
1adjectiveinvalidNot acceptable, because it breaks a rule or fails a legal requirement.~59%
“Your ticket is invalid after midnight.”
synonyms: void, null, unacceptable
2adjectiverejectedRejected by a computer because it has been entered wrongly.~16%
“It kept telling me the password was invalid.”
3adjectivelogicOf an argument, reasoned so that the conclusion does not follow from the premises.~8%
“An invalid argument can still reach a true conclusion by luck.”
4nounweakA person made weak by long illness — an old word, now avoided, and said with the stress on the first syllable.~17%
“In the novel she spends her last years as an invalid.”
Shares are an estimate: a language model read 76 sentences found in the wild and placed 71 of them on a sense (5 were unclear) — a count of our sample, not a measurement of English.
Latin invalidus meant weak: in-, not, laid on validus, strong. Both English words come straight out of it — a ticket that is invalid has no strength in it, and the older noun named a person whose strength had gone. Valid and invalidate are the same Latin muscle.
Proto-Indo-European
*h₂welh₁-
Latin
validus
Middle French
valide
English
valid
English, today
invalid
From in- + valid. valid Borrowed from Middle French valide, from Latin validus. Borrowed from Middle French valide (“healthy, sound, in good order”), from Latin validus, from valeō + -idus, from Proto-Indo-European h₂welh₁- (“be strong”).
Etymology from Wiktionary, CC BY-SA