/ˌɪnvɪˈteɪʃn ||; ˌɪnvəˈteʃən/noun1 [U] the act of inviting sb or being invited 邀请: Entry is by invitation only. 凭请柬入场。a letter of invitation 邀请信
2 [C] an invitation to sb/sth (to sth/to do sth) a written or spoken request to go somewhere or do sth 邀请书；口头邀请: Did you get an invitation to the conference? 你接到会议邀请函了吗？a wedding invitation 婚礼请帖
You may accept an invitation, or you may turn it down or decline it. 接受邀请可以说accept an invitation，拒绝就用turn it down或decline it。