Valid and Efficient

adjective

• Well grounded in logic or truth or having legal force.
  • usage: "a valid inference"; "a valid argument"; "a valid contract"
• Still legally acceptable.
  • usage: "the license is still valid"

• (a.) Having sufficient strength or force; founded in truth; capable of being justified, defended or supported; not weak or defective; sound; good; efficacious; as, a valid argument; a valid objection.
• (a.) Having legal strength or force; executed with the proper formalities; incapable of being rightfully overthrown or set aside; as, a valid deed; a valid covenant; a valid instrument of any kind; a valid claim or title; a valid marriage.
• (a.) Strong; powerful; efficient.

Legally binding; authorized.

adjective

• Being effective without wasting time or effort or expense.
  • usage: "an efficient production manager"; "efficient engines save gas"
• Able to accomplish a purpose; functioning effectively.
  • usage: "people who will do nothing unless they get something out of it for themselves are often highly effective persons...-G. B. Shaw; "effective personnel"; "an efficient secretary"; "the efficient cause of the revolution"
  • synonyms: effective

• (n.) Causing effects; producing results; that makes the effect to be what it is; actively operative; not inactive, slack or incapable; characterized by energetic and useful activity; as, an efficient officer, power.
• (n.) An efficient cause; a prime mover.