不共戴天的敵人是不朽的朋友。

Mortal enemies are immortal friends.

Source: Tatoeba

Sentence Composition

1 不共戴天 bùgòngdàitiān (idiom) (of enemies) cannot live under the same sky; absolutely irreconcilable
=2 的 de
  1. of; ~'s (possessive particle)
  2. (used after an attribute when it modifies a noun)
  3. (used at the end of a declarative sentence for emphasis)
  4. (used after a noun, verb or adjective to form a nominal expression, as in 皮革的 pígéde "one made of leather" or 跑堂儿的 pǎotángrde "a waiter (literally, one who runs back and forth in a restaurant)" or 新的 xīnde "new one")
  5. also pr. dì or di in poetry and songs
=2 的 dī a taxi; a cab (abbr. for 的士 dīshì)
=2 的 dí really and truly
=2 的 dì (bound form) bull's-eye; target
3 敵人 dírén enemy

classifier: 個
=4 是 shì
  1. to be (followed by substantives only)
  2. correct; right; true
  3. (respectful acknowledgement of a command) very well
  4. (adverb for emphatic assertion)
=4 是 shì variant of 是 shì
5 不朽 bùxiǔ to last forever; eternal; enduring
=6 的 de
  1. of; ~'s (possessive particle)
  2. (used after an attribute when it modifies a noun)
  3. (used at the end of a declarative sentence for emphasis)
  4. (used after a noun, verb or adjective to form a nominal expression, as in 皮革的 pígéde "one made of leather" or 跑堂儿的 pǎotángrde "a waiter (literally, one who runs back and forth in a restaurant)" or 新的 xīnde "new one")
  5. also pr. dì or di in poetry and songs
=6 的 dī a taxi; a cab (abbr. for 的士 dīshì)
=6 的 dí really and truly
=6 的 dì (bound form) bull's-eye; target
=7 朋友 péngyou friend

classifiers: 個, 位
=7 朋友 péngyǒu
  1. (archaic) large number of retainers
  2. (archaic, Ming dynasty) designation given by government bureaucrats to Confucian students
  3. designation given by government bureaucrats to Confucian students
  4. large number of retainers