1
a pair of headphones
耳机通常用复数形式 headphones；一副耳机用 a pair of headphones。
I bought a new pair of headphones.
我买了一副新耳机。
耳机
先理解核心含义，再看它在真实句子里的用法。
耳机
earphone
I bought a new pair of headphones.
我买了一副新耳机。
与耳机一起使用的
Used with headphones.
Whenever I ride the bus, I take my headphones with me.
每次坐公交车，我都随身带着耳机。
One headphone stopped working, so I need to buy a new pair.
有一只耳机不响了，所以我需要买一副新的。
She adjusted her headphones before starting the video call.
她在开始视频通话前调整了一下耳机。
耳机通常用复数形式 headphones；一副耳机用 a pair of headphones。
I bought a new pair of headphones.
我买了一副新耳机。
名词作定语时用单数形式，如 headphone jack（耳机插孔）。
This phone has a headphone jack.
这部手机有耳机插孔。
on headphones 表示“戴着耳机”或“用耳机”，也可说 through headphones。
She likes to listen to music on headphones.
她喜欢用耳机听音乐。
Not this
I bought a headphone yesterday.
Use this
I bought headphones yesterday.
headphone 是可数名词，指一副耳机时通常用复数形式 headphones；单数 a headphone 表示一只耳机，不能表示一副。
Not this
I have two headphones.
Use this
I have two pairs of headphones.
当数量超过一且表示“副/对”时，要用 pair of 来计数：two pairs of headphones；直接说 two headphones 会被理解为两只耳机，而不是两副。
Not this
The headphone is too loud.
Use this
The headphones are too loud.
表示一副耳机时需要用复数形式 headphones，谓语动词也要用 are；中文的“耳机”没有单复数变化，所以容易误用单数 is。
Focus on the distinctions below. Other candidates are kept compact until a reliable usage note is available.
耳机插孔
My phone no longer has a headphone jack.
我的手机不再有耳机插孔了。
耳机放大器
He bought a headphone amplifier to improve the sound.
他买了一个耳机放大器来改善音质。
耳机线
The headphone cable is tangled again.
耳机线又缠在一起了。
无线耳机
She prefers wireless headphones for running.
她跑步时更喜欢无线耳机。
降噪耳机
Noise-cancelling headphones are useful on long flights.
降噪耳机在长途飞行中很有用。
一副耳机
I need a new pair of headphones.
我需要一副新耳机。
Use headphone naturally, then get feedback on meaning, tone, grammar, and phrasing.
Revisit a common error or keep this word in your review list.
head（头）+ phone（电话）→ 戴在头上听声音的电话，就是耳机。
语域：neutral 常见场景：日常对话、电子产品说明、音频设备讨论 ‘headphone’ 是中性常用词，日常和正式场合都比较常见；指单只耳机时用单数，指一对耳机时通常用复数形式 ‘headphones’。
Headphone has no common perfect rhymes: the stressed vowel /e/ is followed by /dfəun/, a pattern found in almost no other word. The listed words are useful comparisons: head, bed, and dead share the /-ed/ rime of the first syllable, while telephone, microphone, and cellphone end in the same written '-phone' and the unstressed /fəun/ sound, but they do not rhyme with headphone.
Dictionary facts from ECDICT, WIKTIONARY.