Japanese language question?

So, in Japanese you have a lot of honorifics. Chan would be an honorific for younger girls (ex: Rin-chan from Usagi Drop :) Kun would be an honorific for younger boys. (ex: Domo-kun XD --> but that's not a great ex.) Sorry can be gomennasai, or sumimasen (excuse me/sorry) but it means something slightly diferent than gomennasai.

Chan, used with people you are close too, family members babies, pets, people younger than you etc.

Kun, typically used for boys your age to express closeness without using chan. Rules on this vary, as it can sometimes be used with girls, it is a level of closeness between san and chan

Sama, is a more respectful version of san.

San, respectful way to refer to a person.

All honorifics (above) can be used with family (last) or given (first) names in Japan it is family name, then given name.

Gomen nasai: I am sorry.

Gomen: Sorry

Sumimasen: Excuse me/I am sorry [for bothering you]

Oyasumi nasai: Good night/get some rest

Ohayo gozaimasu: Good morning

Konbanwa: Good evening

Konnichiwa: Good afternoon/hello

I think the chan and kun have been answered pretty well already, so I can tell you about gomennasai and sumimasen.

Gomennasai is when you're apologizing for something you've done. Sumimasen is more of 'excuse me'. You use Sumimasen when you're getting through a large crowd and you're going through a lot of people, you use it when you come late to places or when you want to go into some person's house.

Gomennasai is a lot more sincere than sumimasen, and you use it when you're purely apologizing for something you've done.

Both "chan" and "kun" are honorifics put at the end of names for adressing people that are younger than you. "Chan" is typically used towards young girls, while "kun" is used towards young boys in most cases.