noun
frontier (esp. American frontier)
Refers to the historical American frontier, the edge of settled land, often with a sense of adventure and expansion.
西部開拓時代のフロンティアには多くの危険があった。
There were many dangers on the frontier during the Wild West era.
noun
Used for the cutting edge or unexplored areas of academic, scientific, or technological fields.
この研究は宇宙科学のフロンティアを切り開くものだ。
This research opens up a new frontier in space science.