Sell is a verb and sale is a noun:

I'm going to sell my car and buy a new one.

She's selling bottles of water at the football game.

Yesterday I sold all of my old college textbooks on the internet.

The bookstore is having a Christmas sale - everything is 20% off.

(20% off = 20% discount)

The sales of our new product are slowly increasing.

This watch is normally $100, but it's on sale for $70.

(on sale = there is a discount)

There's also a pronunciation difference between sale and sell.

Benefits of Iceberg lettuce

Caution

Lettuce is a very safe vegetable and has no adverse reaction reported so far.There is only one condition in which large quantities of lettuce are contraindicated: For patients undergoing anticoagulant therapy with vitamin K antagonists (such as warfarin). The high amount of vitamin K, may interfere with the therapy, possibly leading to blood clots formation (thrombosis) and related complications. So be aware if youre on such medication.