若且唯若英文if and only if)係邏輯學上嘅一個概念。如果話「A 係真確,若且唯若 B 係真確」(A is true if and only if B is true),意思即係話[1]

  • 「如果 B 係真,A 都會係真」(充分條件;A is true if B is true)而且
  • 「A 只有喺 B 係真嘅情況下先會係真」(必要條件;A is true only if B is true)。

睇埋

參攷

  1. Copi, I. M.; Cohen, C.; Flage, D. E. (2006). Essentials of Logic (Second ed.). Upper Saddle River, NJ: Pearson Education. p. 197.