Invitatory letter邀请信
"a brief invitatory note"
ADJ（形容词） serving as or conveying an invitation 邀请(之意)的
N（名词） any of various invitations to prayer, such as Psalm 95 in a religious service 宣召曲; 宗教仪式中邀请教徒祈祷的赞美诗，如《诗篇》第九十五篇