I usually say 'died',though if I am aware of the reaction when someone I am talking to, may be negative in the extreme,due to their sensitivity about the word 'died',then I will say 'passed away' out of respect for their feelings.
"Died". I think "passed away" is meant to soften the blow, and I would be careful of what I said if I was actually breaking the news of someone's death to one of their loved ones but otherwise I don't like the expression. I don't know why.
When my husband died, I hated when people used the expression "passed away" or "lost" as if he was a handbag. I aways use the expression "died" as unfortunately that is the hard fact when someone is deceased.
It depends on the person I'm speaking to. I had a 90 year old cousin who used to say "she fell off her perch" which pretty well summed everything up. I've been known to say "he/she had a good innings" for an older individual.
Oh yes....this same cousin also used to use the attractive term "carked it".
By the way....my cousin fell off his perch 3 years ago...but never mind - he WAS 90 so he'd had a good innings.....
I am not happy to use euphemisms and avoid them if at all possible. When my father died, I changed his outgoing phone message to tell people he had died. Not sure my sibs were OK with that but it was my task.
I once had a phone message that stated my sister-in-law was 'gone'. If not for the emotion in the voice, I would have thought she had left my brother.
I use the term died. It may seem blunt to some , but it leaves no room for ambiguity and feels honest. If it seems too harsh I will use passed away.
I notice sometimes people use the term crossed( as to the other side) or passed over. Not keen on either of those. I don't like the term "lost"- it sounds like an act of carelessness.i don't love the term "late" but it can be helpful.