Adjective

(en adjective)

Well grounded or justifiable, pertinent.

*{{quote-magazine, year=2012, month=March-April

, author=(Jan Sapp) , title=Race Finished , volume=100, issue=2, page=164 , magazine=(American Scientist) citation , passage=Few concepts are as emotionally charged as that of race. The word conjures up a mixture of associations—culture, ethnicity, genetics, subjugation, exclusion and persecution. But is the tragic history of efforts to define groups of people by race really a matter of the misuse of science, the abuse of a valid biological concept?}}

I will believe him as soon as he offers a valid answer.

Acceptable, proper or correct.

A valid format for the date is MM/DD/YY.

Do not drive without a valid license.

Related to the current topic, or presented within context, relevant.

(logic) Of a formula or system: such that it evaluates to true regardless of the input values.

(logic) Of an argument: whose conclusion is always true whenever its premises are true.

An argument is valid if and only if the set consisting of both (1) all of its premises and (2) the contradictory of its conclusion is inconsistent.

Adjective

(en adjective)

Suitable]] or fit to be [[rely on, relied on; worthy of dependence or reliance; trustworthy

A reliable witness to the truth of the miracles. -- .

The best means, and most reliable pledge, of a higher object. -- .

According to General Livingston's humorous account, his own village of Elizabethtown was not much more reliable , being peopled in those agitated times by unknown, unrecommended strangers, guilty-looking Tories, and very knavish Whigs. --.

(signal processing, of a communication protocol) Such that either a sent packet will reach its destination, even if it requires retransmission, or the sender will be told that it didn't