To thank is defined as to express gratitude or appreciation.(verb)
An example of to thank is sending flowers to a person who made you dinner.
See thank in Webster's New World College Dictionary
Origin: ME thankien < OE thancian, akin to Ger danken < IE base *tong-, to think > think, L tongere, to know
See thank in American Heritage Dictionary 4
transitive verb thanked, thank·ing, thanks
Origin: Middle English thanken
Origin: , from Old English thancian; see tong- in Indo-European roots.
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