乃是

nǎishì
equivalent to either 是 shì or 就是 jiùshì

CEDICT

  1. (literary) to be none other than
  2. to be none other than

Wiktionary

  1. 却是。为转折语。
  2. 正是。

重編國語辭典

Examples

道德上的恶乃是无知的后果。

Moral evil is the result of ignorance.

Source: Tatoeba

Entry Composition

=1 乃 nǎi
  1. to be
  2. thus
  3. so
  4. therefore
  5. then
  6. only
  7. thereupon
=1 乃 nǎi variant of 乃 nǎi
=2 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)
=2 是 shì variant of 是 shì