Shoulda, woulda, coulda.

Sorry that it's been a while - I've been waiting for some inspiration from a messageboard, and Craigslist just came through yet again.

I often see students and other people write something like this: "I should of taken the expressway home instead of the local road."

The problem is "should of." If we think about the grammatical construction, we realize that it doesn't make sense. "Of" is actually a preposition, and prepositions always need to be followed by a noun, which is called the object of a preposition. For instance, you wouldn't say "I sat under." You'd want to include what you sat under - that's the object of the preposition "under."

When people write "should of", "could of", or "would of", they actually mean to write a contraction: "should've", "could've" or "would've". This means should have. Say the contraction out loud. It sounds like should of. That's why people make the error.

There's never a time when someone should write "should of."