Frequency: The word is one of the 3000 most common words in English.
1.
If you are ~ to something, you disagree with it or disapprove of it.
I am utterly ~ to any form of terrorism...
= against
ADJ: v-link ADJ to n/-ing
2.
You say that two ideas or systems are ~ when they are opposite to each other or very different from each other.
...people with policies almost diametrically ~ to his own...
This was a straight conflict of directly ~ aims.
= opposite
ADJ: oft ADJ to n
3.
You use as ~ to when you want to make it clear that you are talking about one particular thing and not something else.
We ate in the restaurant, as ~ to the bistro.
PHRASE: PHR group