"I am sorry, I did not know."

Translation: Вибачте, я не знав.

[Katja...S]

Я вибачаюсь, я не знала. Possible?

[Vinnfred]

To use feminine - surely possible. To say "вибачаюсь" - well, that's not a preferable way to say that you are sorry. Ending "сь" makes the verb reflexive, so it's like you are trying to forgive youself. This form does exist colloquially, but I would advise against using it. You've just started learning the language, so why learn something that is not really right :)

[Katja...S]

Thank you both! It is just amazing how fast one gets replies to questions in this course. And with an explanation :) I just can't stop studying... I was already thinking that it's time to stop for this evening but since I keep getting replies, I will continue for a few more lessons :D

[Shady_arc]

Well, it is not a recommended form, AFAIK. The correct forms are «вибачте», «пробачайте», «прошу вибачити» and so on.

[TARAMAT]

Sorry Duo, but "probachte' should be also accepted. Both my mom and grandmother are Ukrainian, and I know it for a fact!