This is the 1057th most frequent Russian word.
основной
Main; primary; fundamental.
In this sentence, 'основной' is used as an adjective to describe 'целью' (goal), indicating the primary or most important nature of the goal.
Основной целью компании является улучшение качества продукции.
The main goal of the company is to improve product quality.
Here, 'основной' is utilized to qualify 'принцип' (principle), signifying the fundamental or core nature of the principle.
Его основной принцип в жизни — честность.
His main principle in life is honesty.
In this context, 'основной' modifies 'причиной' (reason), emphasizing the predominant or most significant reason for the failure.