The word 一緒 means together. When it is used with the particle に, it expresses the idea of doing something with someone. It can be used to invite someone to do something with you, for example:
When preceded by the particle と, it shows who you are with or who you are doing something with. So for example you can say:
|I'm going to Hawaii together with my brother next week.||来週、 兄 と 一緒 に ハワイ に 行く。raishuu, ani to issho ni hawai ni iku.|
A common situation you might hear 一緒に in Japan is at a restaurant. The server might ask you how you would like to pay the bill, and ask if you will be paying together or separately:
Note the use of the honorific ご which makes the sentence more polite. You can then answer one of the following:
In the sentences above, you can use either に or で without changing the meaning.