frontier

American  

[fruhn-teer, fron-, fruhn-teer] / frʌnˈtɪər, frɒn-, ˈfrʌn tɪər /

noun

• frontiers
  plural

1. the part of a country that borders another country; boundary; border.

2. the land or territory that forms the furthest extent of a country's settled or inhabited regions.

3. Often frontiers.

   1. the limit of knowledge or the most advanced achievement in a particular field.

      the frontiers of physics.

   2. an outer limit in a field of endeavor, especially one in which the opportunities for research and development have not been exploited.

      the frontiers of space exploration.

4. Mathematics. boundary.

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adjective

1. of, relating to, or located on the frontier.

   a frontier town.

frontier British  

/ ˈfrʌntɪə, frʌnˈtɪə /

noun

1. 1. the region of a country bordering on another or a line, barrier, etc, marking such a boundary

   2. ( as modifier )

      a frontier post

2. 1. the edge of the settled area of a country

   2. ( as modifier )

      the frontier spirit

3. (often plural) the limit of knowledge in a particular field

   the frontiers of physics have been pushed back

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Synonym Usage

See boundary.

Other Word Forms

Derived Forms

• semifrontier
  noun
• frontierless
  adjective
• frontierlike
  adjective
• transfrontier
  adjective

Inflected Forms

Nouns

• frontiers
  plural

Etymology

Origin of frontier

1350–1400; Middle English frounter < Old French frontier, equivalent to front (in the sense of opposite side; see front) + -ier -ier ²

Explanation

A frontier represents uncharted territory. It could be a remote piece of land or a new field of study, but if someone calls it "the frontier," you are challenged to explore it. The noun frontier has several meanings. It can refer to the wilderness at the edge of a settled area (picture covered wagons pushing westward) or it can mean a field of study that has not yet been explored (picture genetically engineering pet dinosaurs). Deriving from "the front line of an army," a frontier can be thought of as an offensive line in a battle — always pushing forward, trying to conquer new territory.

Example Sentences

See Examples For:

frontier frontiers

The meeting followed a series of recent warnings from people inside the industry about the rapidly evolving capabilities of advanced or "frontier" AI models and the regulation needed to keep them in check.

From BBC ● Oct. 10, 2026

Former New York Gov. Andrew Cuomo isn’t the typical face of digital finance, but he has emerged as an unlikely champion for the next frontier in U.S. markets: tokenized stocks.

From The Wall Street Journal ● Oct. 9, 2026

OpenAI’s investors had reportedly tried to compare its annualized revenue with that of rival Anthropic, but because the frontier labs calculate this number differently, that led to inconsistencies, according to the Financial Times.

From MarketWatch ● Oct. 9, 2026

"These investigations exemplify how Artemis and Moon Base are expanding the frontier of lunar exploration, advancing innovative technologies, deepening our understanding of the Moon's environment, and paving the way for future astronaut missions."

From Science Daily ● Oct. 8, 2026

To understand the answer to this paradox, we have to remember that, until 400 B.C., the frontier of Tsushima Strait separated not rich farmers from poor hunter-gatherers but poor farmers from rich hunter-gatherers.

From "Guns, Germs, and Steel: The Fates of Human Societies" by Jared M. Diamond

Although the research focused on two regions of the Amazon, the scientists say its conclusions may also apply to tropical deforestation frontiers elsewhere in the world.

From Science Daily ● Sep. 21, 2026

Actually, I take that back – consulting her most devoted fans will open new frontiers for you.

From Salon ● Aug. 29, 2026

In other words, if you want to be inspired by the frontiers of automotive engineering and solutions-based product design, look to China.

From The Wall Street Journal ● Jul. 11, 2026

Terry says Qantas is conquering "one of the last frontiers in commercial aviation".

From BBC ● Jun. 26, 2026

How mad the frontiers had seemed to Lyo-lyok, and would to Man if he could learn to fly.

From "The Once and Future King" by T. H. White