How to check the word "disaster"?
The word CATASTROPHE came into Russian from the Greek katastropha-coup, overthrow, death. Single root words: catastrophic, catastrophic.
Unstressed vowels A cannot be checked, we remember their spelling.
The word Catastrophe turns out to be a feminine noun and the first declension in which we single out the ending -A: Catastrophe-Catastrophe-Catastrophe.
The stress in it falls on the third syllable: catastrophe.
The root of the word is the morpheme CATASTROPHY-: Catastrophic.
Note that in this root there are two unstressed vowels A at once, and the word itself can be mistakenly written as kotOstrophe.
We cannot check these vowels with the same root words, the word Catastrophe is of Greek origin. The Greek prefix KATA should be remembered, like the whole word, it can be found in the words Cataclysm, Catalepsy and others.