Слово "critical". Англо-русский словарь Мюллера

but one of the most critical parts of the entire thing was the release

“Critical glaciology tool,” Norah said.

Also, with quick, critical eye, she noted a scar on his cheek, another that peeped out from under the hair of the forehead, and a third that ran down and disappeared under the starched collar.

Departure speed from a catapult is highly critical and a variation on order of one percent could double or halve trajectory time, Luna to Terra.

Why is this critical? It's critical because

Those are the critical questions, and what we have learned

And it's because I'm giving you critical data about me.