I'm just a simple sailor, so I use 'dead'. Always.
'Deceased' is far more formal and would be used in a report, in court or in any situation where you wanted to sound a little pompous. I still use 'dead'. ;-)
In exactly the same way, I use 'buy' instead of 'purchase'. They have the same difference. -? does that make sense?)
You will see deceased person used and dead body, so deceased is sometimes used, I believe, when referring to a person and thinking about their character, estate, etc. However, I think there's a lot of sense in the simple sailor approach outlined above. ;-)
Undertakers (people who organize funerals) - at least professionally - always use a euphemism: 'departed'/'deceased'.... (Away from the public eye, among themselves, they quite probably use the opposite [a 'dysphemism' is the word I think :-?] and call a dead body somethhing like a 'stiff', or just a 'job'.) Evelyn Waugh's The Loved One is an interesting and amusing source of information and observation about this - for advanced students, that is.
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