Other forms: thanked, thanking
To thank someone is to tell them you are grateful for what they did. You thank the driver as you step off the bus, you thank your aunt for the socks, you thank the stranger who held the door with his foot.
In practice the plural noun does most of the daily work: thanks, thank you, thanks a lot, no thanks. Thanks to means because of, and it serves good news and bad alike — thanks to her we finished early; thanks to the rain nobody came. You thank someone FOR something, and never "thank to" a person. Thankful is how you feel; a thankless job is one nobody appreciates, like clearing out the office fridge. There is a cold use as well: "I'll thank you to keep your voice down" is not gratitude, it is an order. And thank goodness, thank heavens and thank God are all plain relief.
1verbthankTo tell someone you are grateful for something they did.
“She thanked the nurse twice before she left the ward.”
2verbnameTo name someone or something as the cause of a result, whether the result is good or bad.
“You can thank the roadworks for the extra half hour.”
3nounexpressionAn expression of gratitude, nearly always in the plural.
“He left without a word of thanks.”
Too few real examples of this word to estimate which sense is commonest.
Thank and think are relatives. Old English þanc meant gratitude, and also mind and thought; Proto-Germanic þankaz carried the whole bundle — gratitude, thought, remembrance — and behind it lies the Proto-Indo-European root teng-, "to perceive, to think". To thank someone was to hold them in mind. Dutch dank and German Dank are the same word, still standing where English left them.
Proto-Indo-European
*teng- — to perceive; to think
Proto-Germanic
*þankaz — gratitude; expression of gratitude, thanks; mind, thought; remembrance
Old English
þanc
Middle English
thank — gratitude; expression of gratitude, thanks; attractiveness; commendation, praise; God’s grace; goodwill; merit, reward; mind, thought
English, today
thank
Built from
From Middle English thank (“gratitude; expression of gratitude, thanks; attractiveness; commendation, praise; God’s grace; goodwill; merit, reward; mind, thought”), from Old English þanc, þonc (“gratitude; expression of gratitude, thanks; favour, grace; mind, thought; pleasure, satisfaction”), from Proto-Germanic þankaz (“gratitude; expression of gratitude, thanks; mind, thought; remembrance”), ultimately from Proto-Indo-European teng- (“to perceive; to think”). 2 Cognate with stq Tonk (“thanks”), West Frisian tanke (“thanks”), cim dånke (“thanks”), Dutch dank (“thanks”), German Dank (“thanks”), wym dank, daŋk, daonk (“thanks”), Yiddish דאַנק (“thanks”), Danish tak (“thanks”), ovd tokk (“thanks”), Faroese takk, tøkk (“thanks”), Icelandic takk, þökk (“thanks”), Norwegian Bokmål and Norwegian Nynorsk takk (“thanks”), Swedish tack (“thanks”), Gothic 𐌸𐌰𐌲𐌺𐍃 (“thanks”), xvn þank- (“thanks”); also Latin tongeō (“to know”).
Etymology from Wiktionary, CC BY-SA