crucial

adj

1. Essential or decisive for determining the outcome or future of something; extremely important; vital.

   “The battle of Tali-Ihantala in 1944 is one of the crucial moments in the history of Finland.”

   “A secure supply of crude oil is crucial for any modern nation, let alone a superpower.”

   “The perfume industry is facing a major problem: maintaining constant levels of quality is crucial, but it is increasingly difficult to obtain a regular supply of all the necessary natural ingredients.”

   “Vocabulary provides a foundation from which grammar, phonology, and morphology emerge, and in a subject area it provides access to conceptual knowledge. Vocabulary selection for pedagogical purposes is therefore crucial.”

   “Language is crucial because it is the best weapon against violence. When children don’t have the words to express their thoughts, they raise their fists.”

2. (archaic)Cruciform or cruciate; cross-shaped.
3. (Jamaica, especially, slang)Very good; excellent; particularly applied to reggae music.

   “Delbert Wilkins is the most crucial pirate radio DJ in Brixton.”