valid

The definition of valid is something effective, legally binding or able to withstand objection.

(adjective)

See valid in Webster's New World College Dictionary

adjective

having legal force; properly executed and binding under the law
well-grounded on principles or evidence; able to withstand criticism or objection, as an argument; sound
effective, effectual, cogent, etc.
Rare robust; strong; healthy
Logic correctly derived or inferred according to the rules of logic

Origin: Fr valide < L validus, strong, powerful (in ML, valid) < valere, to be strong: see value

Related Forms:

See valid in American Heritage Dictionary 4

adjective

Well grounded; just: a valid objection.
Producing the desired results; efficacious: valid methods.
Having legal force; effective or binding: a valid title.
Logic
a. Containing premises from which the conclusion may logically be derived: a valid argument.
b. Correctly inferred or deduced from a premise: a valid conclusion.
Archaic Of sound health; robust.