1.Yesterday our team also got an informal invitation to move and participate in a chinese TV league that will go on for two months.
昨天我们队接到了一个非正式邀请，去中国参加一个电视联赛，为期两个月。
2.People will expect an answer even to an informal invitation.
但即使是非正式的邀请，人们也总是希望对此得到答复。
3.He extended an informal invitation to us
他向我们发出非正式邀请。