What is the difference between そうか and そっか?


Is そっか just more slangy? Is そうか the same as saying ああそう? Or, is this more a
spoken thing? If so, what is used when writing?




I think that

  * そうか is "I see", "really?"
  * そっか is "Ah! I see!", "oh! I understand what you meant!", "ORLY?". The interjection kind of reaction.
  * ああそう is "oooooh? I see". This is something I hear often when people are not convinced at all, but are friendly with you, even playing with you. (Say, you were seen with two different girls the same day, your friends say you're picking up too many girls, and you explain "it's not what you think! one was my sister, and the other was showing me the way!". Your friends would then say "ああそう", and attack again: "but you were holding hands!"…)

In writing, you'd just write "そうですか". Writing (in any language) should be more
polite and formal, so as to avoid misinterpretation…

