for sale的意思是“待售”“供出售”，即“用于出售”。on sale有两个意思，一是表示“出售”，与for sale不同，它表示的是“进入销售环节”“处于被销售的状态”；二是表示“廉价出售”“打折出售”。
sale
noun
[mass noun]the exchange of a commodity for money; the action of selling something
卖，出售
we withdrew it from sale.
我们把它撤下不卖了。
the sale has fallen through.
这桩买卖已经告吹。
(sales)a quantity or amount sold.
销售量，销售额
price cuts failed to boost sales.
减价没能增加销量。
(sales)the activity or business of selling products.
销售活动，销售
director of sales and marketing.
销售部主管。
an event for the rapid disposal of goods at reduced prices for a period, especially at the end of a season
（尤指季末的）廉价出售，贱卖
a closing-down sale.
歇业大甩卖。
[often with modifier]a public or charitable event at which goods are sold.
义卖
a public auction.
拍卖
习惯用语
(up) for sale
offered for purchase; to be bought
供出售；待售
cars for sale at reasonable prices.
价位合理的待售小轿车。
on sale
offered for purchase
供出售；上市
the November issue is on sale now.
11月号的杂志现在已经在发售了。
(N. Amer.)offered for purchase at a reduced price.
(北美)削价出售
sale or return
[usu. as modifier](Brit.)an arrangement by which a purchaser takes a quantity of goods with the right of returning surplus goods without payment
(英)剩货包退，可退货经售
booksellers normally order books on a sale-or-return basis.
书商通常根据剩货包退的原则定购图书。
