Thorough describes something that is painstakingly complete, like a thorough search for your missing keys in which you look for them in coat pockets, under the table, in the refrigerator — in every single place you can think of.

Thorough rhymes with "burrow": "THUR-oh." It looks a lot like through but remember thorough is an adjective, so you might use it to describe a thorough investigation or a thorough review. In contrast through is used most often as a preposition — you might look through every drawer, for example, in a search — or as an adverb — you might see a hole in your pocket where coins fall through.

Definitions of thorough

adj painstakingly careful and accurate

“our accountant is thorough
thorough research”
exercising caution or showing care or attention

adj performed comprehensively and completely

“made a thorough search”
exhaustive, thoroughgoing
having every necessary or normal part or component or step

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