invaluable

adj

1. Having great or incalculable value.

   “You are a very strange creature by way of a friend!—always wanting me to play and sing before anybody and everybody! If my vanity had taken a musical turn, you would have been invaluable; but as it is, I would really rather not sit down before those who must be in the habit of hearing the very best performers.”

   “Colonel Cathcart bewailed the miserable fate that had given him for an invaluable assistant someone as common as Colonel Korn. It was degrading to have to depend so thoroughly on a person who had been educated at a state university.”

2. (obsolete)Not valuable; valueless; worthless.

   “The money I have received is so invaluable a sum that I have forborne as yet to pay it in, and am heartily sorry that I cannot better advance His Majesty's service.”

   “It would be an interesting, and far from an invaluable labour, to trace the history of the murrains, or cattle diseases of former days, and there causes and effects.”