* Literal: The pioneers bravely pushed westward, settling the frontier and claiming new lands.
* Figurative: The medical research team is on the frontier of discovering a cure for the disease.
* Abstract: The company's new technology pushes the frontiers of artificial intelligence.
* Descriptive: The vast, uncharted wilderness was a daunting frontier for the explorers.
* Metaphorical: The young artist saw the blank canvas as a frontier of creative possibility.
The best sentence for you will depend on the specific context you need.