When leaving home
The expression 行ってきます is very common, especially in spoken Japanese. While it literally means I will go and then come, which sounds awkward and a little redundant in English, it is totally acceptable in Japanese. It is used mostly by family members, for example when leaving home in the morning to go to work or school. The standard reply to 行ってきます is 行ってらっしゃい, which literally means Go and come back.
|I'm leaving (the house).||いってきます。ittekimasu.|
Literally: I'll go and come back.
|Take care. Come back safely.||いってらっしゃい。itterassyai.|
Literally: go and come back
When returning home
When back home you say ただいま, to which the response is お帰りなさい.
Literally "just now", an abbreviation of "I've returned just now": ただいま帰りました
|Welcome home.||お帰り なさい。okaeri nasai.|
Literally: do return
Before eating you say 頂きます, and after eating you say ご馳走さまでした.
|Bon appétit. (Thank you for the meal)||頂きます。itadakimasu.|
Literally: I humbly receive
|It was a feast. (Thank you for the meal)||ご馳走さま でした。gotisousama desita.|