Question about the particular use of 'か'

Question

1. 今日かあした来てください。 (Please, come today or tomorrow)
2. 行くか行かないか、わかりません。(Go or not, I don't know)

I guess in these two cases 'か' means 'or', but why is there no 'か' after 'あした'. In example 2 there is a 'か' after '行かない'. It is because you are 'counting' the possibilities? Need someone to clear that up for me. Thanks a lot!

Answer 1

Grammatically speaking, か in Sentence 1 and か in Sentence 2 are a bit different.

In Sentence 1, か is simply like "or". In this case, the second か is optional, but is usually omitted in modern Japanese.

• リンゴかバナナ(か)を買う。
• 私か佐藤さん(か)が行きます。

In Sentence 2, the two か's are forming two embedded questions placed in parallel. In this case, か cannot be omitted (but the particle after the か is usually omitted, as described in the link).

• 京都に行くか東京に行くか(を)決めましょう。
• 生きるべきか死ぬべきか、それが問題だ。
  To be or not to be, that is the question.