求翻译：书面邀请是通过写信或发送请帖的形式进行的，比较正式。当然在非常正式的场合要用正式的邀请信或请帖，非正式场合可以使用非正式的邀请方式。是什么意思？

Written invitation is sent by letter or in the form of invitations, and more formal. Of course, in a very formal occasions to use a formal invitation or invitations, where you can use the informal informal invitation.

written invitation is sent through a letter or a form of invitations to more formal. Of course, in very formal occasions to use formal invitation letter or invitation, informal occasions can use informal invitation.

The written invitation is through writes a letter or the transmission written invitation form carries on, quite official.Certainly must use the official invitation letter or the written invitation in the extremely official situation, the unofficial situation may use the unofficial invitation way.

Written invitation is by writing or sending an invitation form, more formal. Course on very formal occasions to use a formal letter of invitation or invitations, non-formal setting you can use the informal invitation.

Written invitation is sent by letter or in the form of invitations, and more formal. Of course, in a very formal occasions to use a formal invitation or invitations, where you can use the informal informal invitation.