אָכֵן

אָכֵן (perhaps from אַח; compare Aramaic דֵּח & דִּכֵּן) adverb with strong asseverative force:
  a. surely, truly, especially at beginning of a speech (stronger & more decided than אַח) Gen 28:16; Exod 2:14; 1Sam 15:32; Isa 40:7; Isa 45:15; Jer 3:23 (twice in verse); Jer 4:10; Jer 8:8. In 1Kgs 11:2 אָבֵן stands unusually; and פֶּןֿ (compare ᵐ5 ᵑ6 ᵑ7) should probably be read (so Klo).
  b. emphasizing a contrast, but indeed, but in fact, especially after אָמַרְתִּי I said or thought, expressing the reality, in opposed to what had been wrongly imagined, Isa 49:4b (opposed to v^a) Isa 53:4 (opposed to vIsa 53:3 end) Jer 3:20 (opposed to the expectation vJer 3:19 b) Zeph 3:7b Ps 31:23b (opposed to vPs 31:23a) Ps 66:19; Ps 82:7 (opposed to vPs 82:6) Job 32:8 (opposed to vJob 32:7).