Efficient and Usable

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.

adjective

• Capable of being put to use.
  • usage: "usable byproducts"
  • synonyms: useable
• Fit or ready for use or service.
  • usage: "the toaster was still functional even after being dropped"; "the lawnmower is a bit rusty but still usable"; "an operational aircraft"; "the dishwasher is now in working order"
  • synonyms: functional, useable, operable, operational
• Convenient for use or disposal.
  • usage: "the house is available after July 1"; "2000 square feet of usable office space"
  • synonyms: available, useable