Ontario

American  

[on-tair-ee-oh] / ɒnˈtɛər iˌoʊ /

noun

1. a province in southern Canada, bordering on the Great Lakes. 412,582 square miles (1,068,585 square kilometers). Toronto.

2. Lake Ontario, a lake between the northeastern United States and southern Canada, between New York and Ontario province: the smallest of the Great Lakes. 193 miles (310 kilometers) long; 7,540 square miles (19,530 square kilometers).

3. a city in southwestern California, east of Los Angeles.

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Ontario British  

/ ɒnˈtɛərɪəʊ /

noun

1. Abbreviation: Ont..   ON.  a province of central Canada: lies mostly on the Canadian Shield and contains the fertile plain of the lower Great Lakes and the St Lawrence River, one of the world's leading industrial areas; the second largest and the most populous province. Capital: Toronto. Pop: 12 392 721 (2004 est). Area: 891 198 sq km (344 092 sq miles)

2. a lake between the US and Canada, bordering on New York State and Ontario province: the smallest of the Great Lakes; linked with Lake Erie by the Niagara River and Welland Canal; drained by the St Lawrence. Area: 19 684 sq km (7600 sq miles)

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Ontario Cultural  

1. Province in central Canada, bordered by Hudson Bay and James Bay to the north; Quebec to the east; the St. Lawrence River, Lake Ontario, Lake Erie, Lake Huron, Lake Superior, and Minnesota to the south; and Manitoba to the west. Its capital and largest city is Toronto.

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Discover More

Ontario is the most heavily industrialized, populous, and prosperous province in Canada.

The Canadian side of Niagara Falls is in southern Ontario.

Ottawa, Canada's capital, is in southeastern Ontario.

Other Word Forms

• Ontarian
  adjective
• Ontaric
  adjective

Example Sentences

See Examples For:

Ontario

The facility in Brampton, Ontario has been closed since 2024 for retooling, to prepare for the production of a next-generation Jeep Compass starting in early 2026.

From The Wall Street Journal ● Aug. 14, 2026

When a wildfire broke out near his First Nation community in northern Ontario, Hubert Wigwas decided to stay put.

From BBC ● Aug. 9, 2026

With his dreams of making it big in the full-time game shattered, Thomas embarked on a remarkable journey across non-league football in England, while there were spells at clubs in Kansas, Ontario, Scotland and Belgium.

From BBC ● Aug. 7, 2026

Notable asset sales this year include Blue Owl Capital’s $1.4 billion sale of loans to asset managers like the California Public Employees’ Retirement System and the Ontario Municipal Employees Retirement System.

From The Wall Street Journal ● Aug. 6, 2026

But also I’m cheesed off because the Art Gallery of Ontario wouldn’t do it.

From "Cat's Eye" by Margaret Atwood