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

“Trey,” was an Atlanta resident who also lived in Ontario and South L.A., prosecutors said.

From Los Angeles Times ● Jul. 17, 2026

The Ontario Provincial Police said 15 communities and their surrounding areas have been evacuated so far.

From Barron's ● Jul. 16, 2026

"This could potentially overtake us here, this has gotten a little scary," a crew member says as the train rushes past burning trees near Armstrong, Ontario.

From BBC ● Jul. 15, 2026

A new branch in Ontario Ranch is scheduled to open July 23, and more openings are planned for later this summer.

From Los Angeles Times ● Jul. 15, 2026

This journey took place in a part of Canada which lies in the northwestern part of the great sprawling province of Ontario.

From "The Incredible Journey" by Sheila Burnford