This is the 465th most frequent Russian word.
смерти
The Russian word "смерти" means "of death" in English.
In this sentence, 'смерти' is the genitive singular form of 'смерть', indicating possession or relation, in this case referring to the concept of death.
Он ничего не боялся, кроме смерти.
He feared nothing except death.
Here, 'смерти' is in the genitive singular case, used to express the cause or origin, in this context referring to the cause of death.
После трагедии они долго обсуждали причины смерти.
After the tragedy, they discussed the causes of death for a long time.
In this case, 'смерти' is the plural genitive form of 'смерть', which is used to imply multiple instances of death.