invalid

From Wiktionary

Word parts[change]

in- + valid

Pronunciation[change]

adjective
noun

Adjective[change]

Positive
invalid

Comparative
none

Superlative
none

  1. Something that is invalid is not valid, meaning it is not correct, appropriate, or acceptable.
    I learned that my credit card was invalid when I tried to pay for dinner with it.

Noun[change]

Singular
invalid

Plural
invalids

  1. Someone who is invalid is very sick, often to the point of having to stay in bed or a wheelchair all the time.
    George Chaffey's invalid wife had to use a wheelchair for the last ten years of her life

Related words[change]