优惠的英文单词怎么写?

楼上说的都对，我在此继续补充几个。
优惠的英文：
preferential
favorable
concession
例句：
1.Domestic preference not applicable.国内优惠不适用。
2.15% off with this flyer凭此宣传品优惠15％
3.Application of preferential income tax rate, and exemption of income tax.适用优惠所得税税率，及所得税免除。
4.For a group of 20 persons or above, room rent is lower (a special rate is available).团体二十人以上，房价优惠。
5.Those who hold the membership card can get a discount on the purchase of cosmetics.
持有会员卡的顾客在购买化妆品时可以享受优惠折扣。
6.On International Children s Day (June 1), we offer children s fast food at a special price. Sampling is welcome.六一节供应儿童快餐，特价优惠，欢迎品尝。