A lecture about English
A linguistics professor was lecturing to his English class one day. "In English," he said, "A double negative forms a positive. In some languages, though, such as Russian, a double negative is still a negative. However, there is no language wherein a double positive can form a negative."

A voice from the back of the room piped up, "Yeah, right."

An elderly patient needed a heart transplant...
An elderly patient needed a heart transplant and discussed his options with his doctor. The doctor said, "We have 3 possible donors; the 1st is a young, healthy athlete who died in an automobile accident, the 2nd is a middle-aged businessman who never drank or smoked and who died flying his private jet. The 3rd is an attorney who died after practicing law for 30 years. Which do you want?""I'll take the lawyer's heart", said the patient. After a successful transplant, the doctor asked the patient why he had chosen the donor he did. "It was easy", said the patient, "I wanted a heart that hadn't been used."