This is good advice

I Used to Have Them Backwards, but I Was Dead Wrong

Professor: What words do we get from the name Aphrodite?
Student #1: Hermaphrodite.
Professor: Yes -- from the union of Aphrodite and Hermes. What else?
Student #2: Aphrodisiac!
Professor: Good! And what is an aphrodisiac?
Students: [Silence.]
Professor: Are you all Victorians? Come on... What's it called when one uses something to arouse sexual appetite?
Student #3: Necrophiliac! [Class laughs.]
Professor: I have to advise you to invest in a dictionary, as it's simply prudent to know the difference between a necrophiliac and an aphrodisiac. Hopefully, you won't ever need to thank me for that.

--NYU

Overheard by: Cairo

via Overheard in New York, Sep 27, 2007