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

The international project brought together researchers from the Wellcome Sanger Institute, the Ontario Veterinary College at the University of Guelph, the University of Bern, and several additional institutions.

From Science Daily • May 24, 2026

She has asked an Ontario court to exempt her from the current law and grant her access to medically assisted dying.

From BBC • May 15, 2026

The company had planned to expand its operations in Alliston, Ontario, about 90 kilometers north of Toronto, where it has been producing conventional vehicles for decades.

From Barron's • May 14, 2026

Ontario says Agnico’s total planned spending and investment in the province is now at C$14 billion by the end of 2030.

From The Wall Street Journal • May 14, 2026

My intention was to creep across the neck of Ontario, bypassing not only Erie but Cleveland and Toledo.

From "Travels with Charley in Search of America" by John Steinbeck