1
the hydra + [verb]
在希腊神话中，许德拉是九头蛇怪；此义可用定冠词 the 或不定冠词 a。
The hydra grew two new heads for each one that was cut off.
这条九头蛇每被砍掉一个头，就会长出两个新头。
九头蛇；许德拉
先理解核心含义，再看它在真实句子里的用法。
九头蛇；许德拉
In Greek mythology, a monstrous snake with nine heads; when one head was cut off, two grew back in its place.
The hydra grew two new heads for each one that was cut off.
这条九头蛇每被砍掉一个头，就会长出两个新头。
A dragon-like creature with many heads and the ability to regrow them when maimed.
Any of several small freshwater polyps of the genus Hydra and related genera, having a naked cylindrical body and an oral opening surrounded by tentacles.
A complex, multifarious problem or situation that cannot be easily and rapidly solved.
The city's traffic problem is a hydra: every new road seems to create congestion somewhere else.
这座城市的交通问题是个九头蛇：每修一条新路，似乎都会在别处造成新的拥堵。
We fixed one error in the system, only to discover the bug was a hydra with many other points of failure.
我们修复了系统里的一个错误，却发现这个故障是个九头蛇，还有大量其他故障点。
Updating the old database has become a hydra, because each change brings new compatibility issues.
更新这个旧数据库已经变成了一个九头蛇，因为每项改动都会带来新的兼容性问题。
在希腊神话中，许德拉是九头蛇怪；此义可用定冠词 the 或不定冠词 a。
The hydra grew two new heads for each one that was cut off.
这条九头蛇每被砍掉一个头，就会长出两个新头。
作星座名时 Hydra 首字母大写，且常与 the constellation 连用。
The constellation Hydra is best seen in spring.
长蛇座在春季最易观测。
比喻义指问题由多个方面构成，难以凭一次努力解决。
The peace process is a hydra of ethnic and religious conflicts.
和平进程是一个由民族和宗教冲突交织而成的难以根除的祸患。
Not this
There are many hydra in the pond.
Use this
There are many hydras in the pond.
hydra 是可数名词，复数形式为 hydras；汉语名词没有复数变化，所以学习者容易漏掉 -s。
Not this
The constellation hydra is in the southern hemisphere.
Use this
The constellation Hydra is in the southern hemisphere.
作“长蛇座”讲时 Hydra 是专有名词，需要首字母大写；小写的 hydra 则指水螅或九头蛇。
Focus on the distinctions below. Other candidates are kept compact until a reliable usage note is available.
（希腊神话中的）勒拿九头蛇
Hercules killed the Lernaean Hydra as one of his twelve labors.
赫拉克勒斯把杀死勒拿九头蛇作为他的十二项功绩之一。
（希腊神话中的）九头蛇
The Hydra grew two new heads for every one that was cut off.
九头蛇每被砍掉一个头，就会长出两个新头。
难以根除的多方面祸患
Poverty is a many-headed hydra that cannot be solved by one policy.
贫困是一个多头祸患，不是一项政策就能解决的。
淡水水螅
The freshwater hydra is often used in studies of regeneration.
淡水水螅常用于再生研究。
长蛇座
The constellation Hydra stretches across the southern sky.
长蛇座横跨南方的天空。
难以根除的腐败祸患
The mayor promised to fight the hydra of corruption.
市长承诺要与难以根除的腐败祸患作斗争。
多头难题；难以根治的复杂问题
Corruption is a hydra-headed problem that will not be solved by one reform.
腐败是一个多头难题，仅靠一场改革无法解决。
……难以根除的祸患
We are fighting the hydra of misinformation on social media.
我们正在与社交媒体上难以根除的虚假信息作斗争。
剪除一端又生出新祸端；斩草未能除根
Banning the product just cut off one of the Hydra's heads; illegal versions soon appeared online.
禁止该产品只是砍掉了九头蛇的一个头，非法版本很快又在网上出现。
九头蛇万岁！
In Captain America: The Winter Soldier, this is the rallying cry of the secret terrorist organization Hydra.
在《美国队长：冬兵》中，这是秘密恐怖组织九头蛇的口号。
Use hydra naturally, then get feedback on meaning, tone, grammar, and phrasing.
Revisit a common error or keep this word in your review list.
联想：水(hydro)里的多头蛇怪，砍掉一头又长两头——所以 hydra 也表示难以根除的祸患。
语域：mixed 常见场景：Greek mythology、formal prose、astronomy、zoology hydra 的用法比较多样：神话和比喻义通常见于较正式的书面语，比喻义多用来指复杂难除的问题；天文学和动物学义项比较常见于专业领域。日常口语中通常较少出现。
复数形式为 hydras，也可写作较罕见的 hydræ。
Dictionary facts from ECDICT, WIKTIONARY.