fundamental mistake

I couldn't believe I had made such a fundamental mistake.

He rarely made fundamental mistakes and never, she suspected, about a man's scientific ability.

The two guards on duty, both young, compounded the problem by each making a fundamental mistake.

This fundamental mistake was, Samantha felt, what had brought all the troubles down upon her head.

I obviously made some fundamental mistakes within the first few days of my move.

He has a group of able ballplayers who consistently make fundamental mistakes.

Despite the success of the system, the pair made some fundamental mistakes.

We believe that on this point there is a fundamental mistake.

I believe that we are making a fundamental mistake.

To understand that is to understand why the mission was a fundamental mistake.