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an orca
orca 为可数名词，单数前用 an，因为其读音以元音 /ɔː/ 开头。
An orca has a large dorsal fin.
虎鲸有巨大的背鳍。
虎鲸；逆戟鲸
先理解核心含义，再看它在真实句子里的用法。
虎鲸；逆戟鲸
a predatory black-and-white toothed whale with a large dorsal fin, common in cold seas
An orca has a large dorsal fin.
虎鲸有巨大的背鳍。
一种海洋哺乳动物(Orcinus orca),与海豚和鼠海豚相关,通常称为虎鲸。
A sea mammal (Orcinus orca) related to dolphins and porpoises, commonly called the killer whale.
We saw an orca breach near the boat during our trip to Alaska.
我们去阿拉斯加旅行时，看到一头虎鲸在船附近跃出水面。
Orcas hunt in groups and are known for their striking black-and-white coloring.
虎鲸成群捕猎，以醒目的黑白配色而闻名。
The children at the aquarium were excited to watch the orca swim in the big pool.
水族馆里的孩子们兴奋地看着虎鲸在大水池中游动。
orca 为可数名词，单数前用 an，因为其读音以元音 /ɔː/ 开头。
An orca has a large dorsal fin.
虎鲸有巨大的背鳍。
定冠词 the 加单数名词可表示整个物种。
The orca is common in cold seas.
虎鲸常见于寒冷海域。
复数形式 orcas 直接加 -s，可用于泛指。
Orcas are black-and-white toothed whales.
虎鲸是黑白相间的齿鲸。
Not this
I saw a orca at the aquarium.
Use this
I saw an orca at the aquarium.
“orca”以元音音素 /ɔː/ 开头，因此不定冠词必须用“an”而非“a”。中文中没有元音/辅音冠词的区别，学习者容易按拼写误用“a”。
Not this
There are several orca in this area.
Use this
There are several orcas in this area.
“orca”是可数名词，复数形式为“orcas”。中文名词没有复数变化，中国学习者常遗漏“-s”，需根据数量使用复数。
Focus on the distinctions below. Other candidates are kept compact until a reliable usage note is available.
虎鲸群
An orca pod swam past the boat.
一群虎鲸游过了小船。
虎鲸幼崽
The orca calf stayed close to its mother.
虎鲸幼崽紧跟着它的妈妈。
野生虎鲸
Wild orcas live in family groups.
野生虎鲸以家庭群体为单位生活。
被圈养的虎鲸
Many people oppose keeping captive orcas in theme parks.
许多人反对在主题公园圈养虎鲸。
虎鲸目击（事件）
There was an orca sighting near the coast.
海岸附近有人目击到了虎鲸。
《魔鲸》
The 1977 horror film Orca tells the story of an orca that seeks revenge on fishermen.
1977年的恐怖片《魔鲸》讲述了一头逆戟鲸向渔民复仇的故事。
Use orca naturally, then get feedback on meaning, tone, grammar, and phrasing.
Revisit a common error or keep this word in your review list.
orca 读作“奥卡”，想象黑白配色的大虎鲸在冷水里竖起背鳍，像穿燕尾服的“海洋霸主”。
语域：neutral 常见场景：海洋生物学、自然纪录片、动物保护讨论 通常用于书面或较正式的语境，口语中更常说 killer whale，但在自然纪录片和科普文章中也很常见。
Walker, talker, and stalker rhyme with orca (/ˈɔːkə/) in non-rhotic (British) pronunciation. Orchid, orchestra, and organ share the initial 'or' spelling and /ɔː/ sound, but their endings differ, so they are lookalikes, not rhymes.
Dictionary facts from ECDICT, WIKTIONARY.