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a swift
swift 是可数名词，指雨燕；复数形式为 swifts。
A swift flew over the river.
一只雨燕飞过河面。
雨燕
先理解核心含义，再看它在真实句子里的用法。
雨燕
A small bird that resembles a swallow and is noted for its rapid flight.
A swift flew over the river.
一只雨燕飞过河面。
一种纯色小鸟,属于雨燕科,类似燕子,以飞行迅速著称。
A small plain-colored bird of the family Apodidae that resembles a swallow and is noted for its rapid flight.
美国肉类包装商,开始使用冷藏火车车厢(1839-1903)
United States meat-packer who began the use of refrigerated railroad cars (1839-1903)
Any of certain lizards of the genus Sceloporus.
出生于爱尔兰的英国讽刺作家(1667-1745)
an English satirist born in Ireland (1667-1745)
A swift flew past our window at dusk.
黄昏时一只雨燕从我们窗前飞过。
We watched the swifts circling high above the lake.
我们看着雨燕在湖面上空高高盘旋。
The swift darted into its nest under the eaves.
雨燕迅速钻进屋檐下的巢里。
swift 是可数名词，指雨燕；复数形式为 swifts。
A swift flew over the river.
一只雨燕飞过河面。
复数形式可泛指雨燕这类鸟。
Swifts spend most of their lives in the air.
雨燕一生中大部分时间都在空中度过。
A flock of swifts circled the tower at dusk.
黄昏时一群雨燕在塔楼周围盘旋。
Not this
I saw swift in the sky.
Use this
I saw a swift in the sky.
swift 是可数名词，单数形式前必须加冠词 a/an。汉语中名词没有冠词概念，所以学习者常漏掉 a。这里表示“一只雨燕”，应说 a swift。
Not this
The swift flew swift.
Use this
The swift flew swiftly.
修饰动词 flew（飞）要用副词 swiftly，而不用形容词 swift。英语中副词通常由形容词加 -ly 构成，形容词不能修饰动词。
Not this
I saw two swift in the sky.
Use this
I saw two swifts in the sky.
swift 是可数名词，复数形式为 swifts。汉语名词没有复数变化，所以学习者常遗漏 -s。数词 two 后必须用复数形式。
Focus on the distinctions below. Other candidates are kept compact until a reliable usage note is available.
普通雨燕
The common swift spends almost its entire life in the air.
普通雨燕几乎一生都在空中度过。
烟囱雨燕
Chimney swifts often roost inside old brick chimneys.
烟囱雨燕经常在旧砖砌烟囱里栖息。
一群雨燕
A flock of swifts circled high above the rooftops.
一群雨燕在屋顶上空高高盘旋。
雨燕的巢
We found a swift's nest under the bridge.
我们在桥下发现了一个雨燕的巢。
雨燕的种类
This region has several species of swift.
该地区有好几种雨燕。
仓促喝一杯；快速喝一杯
He went to the bar for a swift one before the show.
他去看演出前先到酒吧匆忙喝了一杯。
疾如风；快如风
The messenger was as swift as the wind and delivered the news by dawn.
信使快如风，黎明前就送到了消息。
促使行动的刺激；激将
What he needs is a swift kick in the pants to get him started.
他需要有人踹他一脚，促使他行动起来。
太过迅疾，终究与太过缓慢同样迟滞。
The swift is a small bird that catches insects in mid-air.
雨燕是一种在空中捕食昆虫的小鸟。
Use SWIFT naturally, then get feedback on meaning, tone, grammar, and phrasing.
Revisit a common error or keep this word in your review list.
雨燕叫 swift：外形像燕子，却以飞行迅速著称；把 swift 和'快'联想在一起，就记住了这种鸟。
语域：neutral 常见场景：birdwatching、nature writing、animal documentaries 作“雨燕”讲时是普通中性词，多用于观鸟、自然写作或动物科普中；日常对话里提到 swift 时通常需要上下文表明是指鸟。
指鸟时可数，指人名/书名时不可数。
Dictionary facts from DICTIONARY_API_DEV, ECDICT, WIKTIONARY.