Frequency: The word is one of the 1500 most common words in English.
1.
Something that is ~ is needed in order for something else to happen.
I kept the engine running because it might be ~ to leave fast...
We will do whatever is ~ to stop them...
Is that really ~?...
Make the ~ arrangements.
? un~
ADJ: oft it v-link ADJ to-inf
2.
A ~ consequence or connection must happen or exist, because of the nature of the things or events involved.
Wastage was no doubt a ~ consequence of war...
Scientific work is differentiated from art by its ~ connection with the idea of progress.
ADJ: ADJ n
3.
If you say that something will happen if ~, when ~, or where ~, you mean that it will happen if it is ~, when it is ~, or where it is ~.
If ~, the airship can stay up there for days to keep out of danger...
The army needs men who are willing to fight, when ~...
All the rigging had been examined, and renewed where ~.
PHRASE: PHR with cl