Frequency: The word is one of the 3000 most common words in English.
1.
Worst is the superlative of
bad.
2.
Worst is the superlative of
badly.
3.
The worst is the most unpleasant or unfavourable thing that could happen or does happen.
Though mine safety has much improved, miners' families still fear the worst...
The country had come through the worst of the recession.
? best
N-SING: the N, oft N of n
4.
Worst is used to form the superlative of compound adjectives beginning with 'bad' and 'badly'. For example, the superlative of 'badly-affected' is 'worst-affected'.
5.
You say worst of all to indicate that what you are about to mention is the most unpleasant or has the most disadvantages out of all the things you are mentioning.
The people most closely affected are the passengers who were injured and, worst of all, those who lost relatives.
PHRASE: PHR with cl
6.
You use at worst or at the worst to indicate that you are mentioning the worst thing that might happen in a situation.
At best Nella would be an invalid; at worst she would die...
PHRASE: PHR with cl/group
7.
When someone is at their worst, they are as unpleasant, bad, or unsuccessful as it is possible for them to be.
This was their mother at her worst. Her voice was strident, she was ready to be angry at anyone.
PHRASE: n PHR, PHR after v, v-link PHR
8.
You use if the worst comes to the worst to say what you might do if a situation develops in the most unfavourable way possible. The form if worst comes to worst is also used, mainly in American English.
If the worst comes to the worst I guess I can always ring Jean...
He was asked whether he would walk out if the worst came to the worst.
PHRASE: V inflects, PHR with cl