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treat

verb with object
1. behave toward or deal with in a certain way:
〖treat A+副詞〗 〈人が〉A〈人・動物・物など〉を扱う, 待遇する(deal with) (!〖副詞〗は様態の表現)
e.g. she had been brutally treated
e.g. he treated her with grave courtesy.
(treat something as) regard something as being of a specified nature with implications for one's actions concerning it:
〖treat A as C〗 〈人が〉A〈考え・言動など〉をCだとみなす (!Cは〖名詞〗〖形容詞〗)
e.g. the names are being treated as classified information.
〖treat A+副詞〗 〈人が〉A〈事件・問題など〉を扱う, 取り上げる, 論じる(deal with, discuss) (!〖副詞〗は様態・程度の表現)
e.g. the lectures show a striking variation in the level at which subjects are treated.
〖treat A with B〗 B〈薬〉でA〈患者・病気・けが〉を治療する; 〖treat A with B〗 A〈人〉のB〈病気など〉を治療する
e.g. the two were treated for cuts and bruises.
3. apply a process or a substance to (something) to protect or preserve it or to give it particular properties:
〖通例be ~ed〗 〈物が〉 【薬品などで】(化学)処理される «with»
e.g. linen creases badly unless it is treated with the appropriate finish.
4. (treat someone to) provide someone with (food, drink, or entertainment) at one's own expense:
〖treat A to B〗 〈人が〉A〈人・自分自身〉にB〈飲食物など〉をおごる, AをBでもてなす; (買収のために)〈選挙民など〉を供応する
e.g. the old man had treated him to a drink or two.
give someone (something) as a favor:
e.g. he treated her to one of his smiles.
(treat oneself) do or have something that gives one great pleasure:
e.g. treat yourself—you can diet tomorrow.
5. no object negotiate terms with someone, especially an opponent:
⦅かたく⦆ 〈人が〉 «人と/…のことで» 交渉, 折衝する «with/for»
e.g. propagandists claimed that he was treating with the enemy.

noun
an event or item that is out of the ordinary and gives great pleasure:
〖通例a ~〗 もてなし, お楽しみ, ごほうび; うれしいこと, 楽しいこと
e.g. he wanted to take her to the movies as a treat.
used with a possessive adjective to indicate that the person specified is paying for food, entertainment, etc., for someone else:
⦅話⦆ ; 〖one's ~〗 おごり, おごる番
e.g. “My treat,” he insisted, reaching for the bill.

PHRASES
—— a treat British informal
used to indicate that someone or something does something specified very well or satisfactorily:
e.g. their tactics worked a treat.
used to indicate that someone is looking attractive:
e.g. he looked a treat in his suit and bowler hat.

DERIVATIVES
treater noun

ORIGIN
Middle English (in the senses ‘negotiate’ and ‘discuss a subject’): from Old French traitier, from Latin tractarehandle’, frequentative of traheredraw, pull’. The current noun sense dates from the mid 17th century.