Sector - includes many industries - e.g. Agriculture, Technology
Industry group - group of industries - e.g. Restaurants
Industry - e.g. Type of restaurants such as fast food restaurants
Consider language:
If your product or service is too specific, broaden to use a word(s) that include similar products.
There may be other terms that are more popular - be sure to include other terms in your industry research.
Places to look for language:
Articles about the industry (in online collections such as Canadian Newsstream: Major Dailies and ABI/Inform, or market research reports from such collections as Passport (GMID) and IBISWorld).
NAICS Canada is an industry classification tree - all industry numbers group industries and name similar industrial activities. See the NAICS Classification Manual.