Grammar Girl here. Today’s topic is “cement” versus “concrete.”

But first, this podcast is brought to you by LivePerson.com. LivePerson.com a world of experts.

Guest writer Sal Glynn writes:

Accuracy is important. You might think concrete and cement are interchangeable, but you'll quickly find that you're mistaken when some guy at Home Depot rolls his eyes at you when you ask for the wrong thing. And if you're writing instructions for someone and you use the wrong word, it'll be your fault when things don't go so well. Yes, “cement,” and “concrete” have completely different meanings (1), and knowing what they are helps you use them well and maintain your dignity in home improvement stores.

The History of Cement and Concrete

Cement comes from the Latin word “caementum,” meaning rough-cut stone, while concrete is from the Latin word “concretus,” meaning to grow together or harden. Both words wandered through Middle English until they met in 1756, when John Smeaton used his version of cement in rebuilding the Eddystone lighthouse.

In 1824 Joseph Aspdin patented “Portland cement,” a powder made of limestone and clay. He called it Portland cement because when it was mixed with sand, gravel, pebbles, bits of rock, and water, the resulting dried concrete resembled the limestone from the English Isle of Portland.

This is the division: cement is a powder that is mixed with other materials and water to create the solid mass known as concrete. There is no such thing as a cement overpass, a cement porch, or a cement pond. These are all concrete. If you stub your toe on concrete you'll yell like a Cretin. Get it? Concrete. Cretin.

And in case you were wondering, pavement is also not concrete. Pavement is a solid material made of sand, gravel, or crushed stone much like concrete, but the cement binder is replaced with asphalt or tar.

Uses and Abuses of Concrete

Cement does have other meanings that don't relate to construction, for example,

Henrik and Daphne cemented their relationship by exchanging nose rings.

The transitive verb “cemented” means to bind or join together. Henrik and Daphne swap nose rings to show they are more than casual friends.

The idiomatic use of “cement” to mean “determined or unalterable” is wrong. For example, it would be wrong to say

Daphne’s opinions about firearm safety and tattoos were set in cement.

At best, that means Daphne’s opinions were set in powder. Since she refused to be swayed, her opinions were set in concrete.

That Other Kind of Concrete

Outside of building materials, “concrete” is the opposite of “abstract,” and means actual or specific things. An automobile is concrete, while justice is abstract. Here's how you'd use it in a sentence:

Henrik talked about building a summer home, but none of his plans were concrete.

Plans are abstract when they aren't specified or put in motion. Henrik needs to make a decision and get to work instead of sitting around talking.

[Web Bonus] More Concrete for the Curious

The French avant-garde “musique concrète” (2) began in the late 1940s with composer Pierre Schaeffer. The music ignores the abstract of sharps and clefs in composition and instead uses sound from objects like tin cans to power drills. These are recorded on tape and altered to create music. Noted recent composers in this genre include Steve Reich, Negativland, and Frank Zappa.

Concrete poetry (3) does away with old stuff like straight lines and syntax, and sets the words in kinetic aggregate of collage, different typefaces, graphics, and calligraphy to create levels of meaning not previously available from the printed page. Scottish artist and poet Ian Hamilton Finlay sculpts his concrete poems. For more on concrete poetry, visit the Sackner Archive of Concrete and Visual Poetry at www.rediscov.com/sacknerarchives/

Now that you understand the difference between cement and concrete, remember the quick and dirty tips is that you cement things together, and stub your toe on concrete.

Keep listening after this message from our sponsor for information about how you can participate in the Grammar Girl Pet Peeve of the Year contest.

Pet Peeve of the Year Contest

In a month or so I'll be announcing the Grammar Girl Pet Peeve of the Year, and it will be based entirely on your input. Let me know what irritated you the most about language in 2008 by leaving a comment on the transcript for this episode at QuickandDirty Tips.com. It can be anything -- a phrase, a new word, an omission – whatever it was that stood out to you as a problem with language this year. Again, leave a comment in the transcript at QuickAndDirtyTips.com.

The Dog Walked Down the Street: An Outspoken Guide for Writers Who Want to Publish

This episode was written by guest-writer Sal Glynn, the author of the award-winning book The Dog Walked Down the Street, An Outspoken Guide for Writers Who Want to Publish. Find out more about Sal at his blog, http://dogwalkeddownthestreet.blogspot.com. And I'm Mignon Fogarty, author of the paperback book Grammar Girl's Quick and Dirty Tips for Better Writing, which makes a lovely and affordable gift. I think books in general make great gifts. I often to give books. But I guess that wouldn't surprise anyone!

That's all. Thanks for listening.

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