In the slippery world of “affect versus effect” many default to the “affect is a verb and effect is a noun” thought process. But both words can be used as both noun and verb, which makes choosing the right word in this manner a matter of gut-feeling guesswork. This dilemma is explained well in a blog post from PoynterOnline.

Roy Peter Clark, who often writes the “Writing Tools” column, defines the words and then offers his own trick for deciding which one is correct: Clark’s Wager, a play on Pascal’s Wager, is a pseudo-scientific theory that “explains” the difference between “affect” and “effect.”

Clark writes: “When it comes to noun forms, I bet on “effect,” because it is more common. But with the verb forms, I’ll wager on “affect,” because “chances are” I’ll be correct. I’m not bragging about this, believe me. I’ve used the same dodgy approach to commas, periods and quotations marks.”

But this method doesn’t work all of the time, so Clark also offers eight tips to help those writers that don’t want to gamble with their prose:

• As a noun “effect” is more common than “affect.”
• The noun “effect” means “that which is caused.”
• The noun “affect” refers to the face we show the world.
• The verb “affect” is more common than “effect.”
• The verb “affect” means “to influence.”
• The verb “effect” means “to bring about” and is often used with the object “change.”
• In a crunch, use Clark’s Wager: bet on the most common usage.
• If you bet wrong, be ready to thank a copy editor for saving your ass.