Student or Learner
How to understand the "for" in this sentence, is it necessary?
The prognosis after the operation was for a full recovery.
Thanks a lot
A prognosis, like a forecast, is the report itself. If we want to know what the actual future situation will be, we usually use for.
We often omit for, especially in informal speech.
ps. "How to understand..." is also fairly informal, except in headlines or titles. "How do/should we understand..." is better.