2 sentences

1. 你有邀请函吗？

   nǐ yǒu yāo​qǐng​hán ma?

   Do you have an invitation?

   Source: OpenSubtitles

2. 他发来了一封正式的邀请函。

   tā fā​lái le yī fēng zhèng​shì de yāo​qǐng​hán.

   He sent a formal invitation letter.

   Source: Dong Chinese Dictionary