Frequency: The word is one of the 3000 most common words in English.
1.
If you describe something or someone as ~, you mean that they are very useful and helpful.
Many of our teachers also have ~ academic links with Heidelberg University...
The experience was very ~.
ADJ
2.
Valuable objects are objects which are worth a lot of money.
Just because a camera is old does not mean it is ~.
...~ books.
ADJ