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put a hairpin in one's hair
put + 名词 + in/into one's hair 表示“把……夹/别在头发里”。
She put a hairpin in her hair before going out.
她出门前在头发上别了一个发夹。
发夹；发簪；夹发针
先理解核心含义，再看它在真实句子里的用法。
发夹；发簪；夹发针
hairpin
She put a hairpin in her hair before going out.
她出门前在头发上别了一个发夹。
发夹；发卡
A pin or fastener for the hair.
用于固定女性头发的双齿发夹
a double pronged pin used to hold women's hair in place
一种核酶,即发夹状核酶
A kind of ribozyme; hairpin ribozyme.
道路上的U形急转弯；发夹弯
A very tight bend in a road; a hairpin bend.
She used a hairpin to keep her bun in place.
她用一根发夹把发髻固定住。
Her hairpins were scattered all over the dressing table.
她的发夹散落在梳妆台上。
I need to buy some hairpins for my sister's wedding.
我需要为妹妹的婚礼买一些发夹。
put + 名词 + in/into one's hair 表示“把……夹/别在头发里”。
She put a hairpin in her hair before going out.
她出门前在头发上别了一个发夹。
use sth to do sth 表示“用某物做某事”，to 后接动词原形。
You can use a hairpin to secure loose strands.
你可以用发夹固定松散的头发。
with a hairpin 是方式状语，说明使用的工具。
She held her hair in place with a hairpin.
她用发夹把头发固定住。
Not this
I bought hairpin yesterday.
Use this
I bought a hairpin yesterday.
hairpin 是可数名词，单数形式前必须加冠词 a/an。中文没有冠词概念，学习者常遗漏，需记住可数名词单数不能裸用。
Not this
She wears two hairpin in her hair.
Use this
She wears two hairpins in her hair.
hairpin 是可数名词，复数形式为 hairpins。two 等数字后必须使用复数，不能省略 -s。
Not this
She put a hairpin on her hair.
Use this
She put a hairpin in her hair.
英语中 hairpin 等夹在头发里的发饰用 in one's hair，表示“在头发里”，而不是用 on。中文“在头发上”直译成 on 是典型错误，需注意固定搭配 in。
Focus on the distinctions below. Other candidates are kept compact until a reliable usage note is available.
戴发夹
She wore a pearl hairpin to the wedding.
她戴着珍珠发夹去参加婚礼。
别上发夹
He watched her put in a hairpin before going out.
他看着她出门前别上发夹。
取下发夹
She pulled out a hairpin and let her hair fall.
她取下发夹，让头发披散下来。
一盒发夹
I bought a box of hairpins at the store.
我在商店买了一盒发夹。
金属发夹
A metal hairpin can hold thick hair better than a plastic one.
金属发夹比塑料发夹更能固定浓密的头发。
U形急转弯，发夹弯
The mountain road has a dangerous hairpin turn.
那条山路有一个危险的U形急转弯。
发夹形弯道，U形急弯
Drivers must slow down at the hairpin bend.
司机在发夹形弯道必须减速。
U形曲线，发夹弯
The narrow hairpin curve is difficult for large trucks.
这个狭窄的发夹弯对大型卡车来说很难通过。
Use hairpin naturally, then get feedback on meaning, tone, grammar, and phrasing.
Revisit a common error or keep this word in your review list.
联想 hair（头发）+ pin（别针）：像别针一样插进头发里固定发髻的东西，就是发夹。
语域：neutral 常见场景：日常梳妆、美发用品、时尚搭配 通常为中性词，日常口语和书面描述中都较常见，多用于谈论发型、梳妆或美发用品。
hairpin 读作 /ˈheəpɪn/，由 hair /heə/ 和 pin /pɪn/ 组成。hair、haircut 以 /heə/ 开头，与 hairpin 的第一部分同音；pin、pushpin、pinball 含 /pɪn/，与 hairpin 的第二部分同音。hair 和 pin 都不与整个 hairpin 押韵。注意 turnip 虽以 -nip 结尾，但读 /ˈtɜːnɪp/，不是 /pɪn/，也不与 hairpin 押韵。
Dictionary facts from ECDICT, WIKTIONARY.