Is there a special word for a death anniversary? For example a birth anniversary would be a "birthday", but what would a death anniversary be?
The word for a death anniversary is... anniversary.
anniversary noun an·ni·ver·sa·ry | \ˌa-nə-ˈvərs-rē,-ˈvər-sə-\
the annual recurrence of a date marking a notable event
In the instance of a death, you would modify it with a prepositional expression. An example would be:
There are plans to release a film about his life next year, which would mark the tenth anniversary of his death.
We usually associate anniversary with marriages or work tenure, but the term is etymologically agnostic to those distinctions. Much like there isn't a special word for "sports car" (outside of the actual names of cars, like Ferrari, or Lamborghini); it's just a car that's intended for the sport of driving.
English has not accommodated in wide use any of the other answers suggested so far (deathday*, deathiversary, heavenly birthday, yahrzeit). [*deathday, is a lazy portmanteau. Its history only attests to its obsolescence, and it is in the bottom 20% of looked-up words, and an uncommon expression. ]
One word for this is deathday (a word which dates back to Old English, in fact):
the day or the anniversary of the day of a person's death.
Dictionary.com Unabridged. Based on the Random House Dictionary, © Random House, Inc. 2018
One well-known example is the deathday party that Nearly Headless Nick has (Harry Potter and the Chamber of Secrets, Chapter 8: "The Deathday Party").
In informal contexts, the word that's generally used is deathiversary (also sometimes spelled death-iversary):
the anniversary of someone's death
I am eating neapolitan ice cream all day today in honor of my dad's 2 year deathiversary.
Urban Dictionary (definition by Miss Jaimie)
Although the entry on UD doesn't have a lot of upvotes, the word is easy to understand. It's also fairly widespread. Here are some examples:
- 5 Ideas for Facing Deathiversaries - Modern Loss
- Aggronautix Unveils GG Allin 25th Deathiversary Bust - PopHorror
- Shakespeare's 400th “Deathiversary”: His Best Death Scenes Ever
- #deathiversary on Twitter
- Results in Google News
- Assorted Google Books examples:
The only word I know that matches this is very specific:
(pronunced 'yar tsayt' = /'jar tsait/) is an anniversary of someone's death, usually a close relative. But it is specifically used only in the context of a Ashkenazi Jewish memorial. The word is from Yiddish (close to German) for 'year time'.
There is no similarly on-point word in English for an anniversary of a death outside of the Jewish tradition.
One term which is used, particularly in some forms of Christianity, is heavenly birthday — the day the person appeared in heaven — to contrast the day with the earthly birthday when they appeared on earth.
If it was a birthday celebration, it was Christ's heavenly birthday, not his earthly one, which was being celebrated ...
For example, young children may commemorate a sibling's ''heavenly birthday'' by lighting candles and sharing memories of the deceased.
The Assumption is important to many Catholic and Orthodox Christians as the Virgin Mary's heavenly birthday (the day that Mary was received into Heaven).
This wouldn't necessarily be appropriate for in all religions, and not all branches of Christianity either. And humanists would disagree about an afterlife at all.