1. 邀请
    An invitation is a written or spoken request to come to an event such as a party, a meal, or a meeting.

    e.g. ...an invitation to lunch...
           共进午餐的邀请
    e.g. The Syrians have not yet accepted an invitation to attend...
           叙利亚人还没有接到出席邀请。

2. 请帖;请柬
    An invitation is the card or paper on which an invitation is written or printed.

    e.g. Hundreds of invitations are being sent out this week.
           本周将寄出数百份请柬。
    e.g. ...gold embossed invitation cards.
           烫金的请柬

3. 诱因;招致…的行为
    If you believe that someone's action is likely to have a particular result, especially a bad one, you can refer to the action as an invitation to that result.

    e.g. ...a war that most liberal Democrats regarded as an invitation to disaster...
           一场大部分自由民主党人认为会招致灾难的战争
    e.g. Don't leave your shopping on the back seat of your car — it's an open invitation to a thief.
           别把买的东西放在汽车后座上——那会招来小偷的。