invaluable
adj.adj. extremely useful or important. It means something is so valuable that you cannot put a price on it.
adj. of extremely great worth or importance; indispensable. Often confused with 'valuable' (which implies a high monetary price), but 'invaluable' emphasizes that the item is priceless.
Your help was invaluable to our success.
The old maps were invaluable for understanding how the city changed over the last century.
While the painting was valuable in a financial sense, its historical significance made it truly invaluable to the museum's collection.
From in- + valuable (compare priceless).
Do not confuse with 'valuable'. 'Valuable' means worth a lot of money; 'invaluable' means too important to be measured by money.
an invaluable mistakea valuable mistake'Invaluable' means extremely useful, not 'not valuable'. Use 'worthless' or 'valueless' for things with no worth.