Describing size or extent:
* The vast desert stretched as far as the eye could see.
* The library housed a vast collection of ancient texts.
* The company's vast network of suppliers spanned the globe.
Describing knowledge or experience:
* She possessed a vast knowledge of history and literature.
* He had vast experience in the financial industry.
Describing an overwhelming feeling:
* The vast emptiness of the universe filled me with a sense of awe.
* The vast possibilities of the future were both exciting and daunting.
Figurative uses:
* The vast ocean of information available online can be overwhelming.
* She had a vast capacity for love and compassion.