In my experience, the terms 'patient' and 'casualty' tend to be used pretty interchangeably when referring to people in need of medical attention. However, I feel like there's definitely a semantic difference between the two - I just can't quite figure out what it is.
I think any difference might be based on either:
- where the person is in the chain of care (i.e. a casualty becomes a patient once medical care is provided);
- the type of issue the person is facing (i.e. 'casualty' would refer to acute trauma or injury whereas a 'patient' would be someone with a chronic condition being treated over a long period of time); or
- as a relation (i.e. a casualty exists on their own, a patient must be a patient of someone like a doctor).
Or maybe I'm mistaken and there is no functional difference.
The only thing I could find online is this WikiDiff which defines a 'patient' as:
A person or animal who receives treatment from a doctor or other medically educated person.
and 'casualty' as:
A person suffering from injuries or who has been killed due to an accident or through an act of violence.
Which seem to suggest there is a difference, but it seems to straddle all of the differences I proposed (whilst also suggesting that non-human animals can be patients but not casualties).