Proper Punctuation for Appositive Phrases

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When two terms that mean the same thing are introduced in succession in a sentence, careless writers, by omitting a crucial comma, often imply that the definition of the terms is in fact distinct. Here are some examples of misleading statements, plus discussions and revisions.

1. “Sunlight is a mixture of different colors or wavelengths, which combine to form white light.”
Colors and wavelengths are, for practical purposes, the same thing, but “colors or wavelengths” implies otherwise. To signal that wavelengths is an alternative term for colors, it should be set off in an appositive phrase: “Sunlight is a mixture of colors, or wavelengths, that combine to form white light.” (Notice, too, the replacement of which with that and the deletion of the comma that followed it — not all colors, or wavelengths, combine to form white light; only these do. I also deleted the usually superfluous adjective different.)

2. “Its odd properties are essential for the evolution and survival of life on Earth, particularly given its ability to form a weak connection called a hydrogen or H-bond.”
The weak connection is not called a hydrogen or H-bond, and it does not have the alternative names hydrogen and H-bond, both of which possibilities are suggested by this statement; the choices are “hydrogen bond” and H-bond.

To indicate that H-bond is a distinct term, that it is not an alternative to hydrogen alone, and that it is an abbreviation of “hydrogen bond” requires a minimal pair of corrections: the use of the full phrase “hydrogen bond” and the insertion of a comma after that phrase. The revision is “Its odd properties are essential for the evolution and survival of life on Earth, particularly given its ability to form a weak connection called a hydrogen bond, or H-bond.”

3. “Then, as that part of Earth passes out of the gravitational bulge, the tide goes out or ebbs.”
Again, the lack of a comma between two terms separated by or implies distinct meanings (suggesting that going out and ebbing are different actions), but this sentence, in describing a scientific phenomenon, explains a process and then supplies a perhaps unfamiliar synonym, so a comma should divide them.

But there’s another problem — one that I haven’t seen discussed in writing guides or grammar handbooks but that has always bothered me: Why, when introducing a new term, supply the better-known synonym or a definition first — what’s the use of including the new term if it’s not presented before the aid to comprehension?

It seems more logical to provide the new term first, then provide context: “Then, as that part of Earth passes out of the gravitational bulge, the tide ebbs, or goes out.” (The second example in this post at least positions the appositive terms sensibly, and the first example does not apply, as one term does not define the other, as here, or clarify it, as in the second example.)

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6 thoughts on “Proper Punctuation for Appositive Phrases”

  1. The above is an EXCELLENT article! Thank you very much, Mr. Nichol.

    Also, this article demonstrates not only poor use of the language, but also the quite poor level of science education in our schools and colleges nowadays among the general student body (not those who major in college in the physical sciences, engineering, architecture, etc.). I know that it is bad in the United States, but my friends in England have told me that it is worse there.

    When it comes to electromagnetic radiation of any kind – including light and radio waves – there is this straighforward relationship:
    In free space, or in the atmosphere, multiply the wavelength by the frequency, and you always get the speed of light. (That’s about 300,000 kilometers per second in round numbers.) In other words, the wavelength and the frequency are “inversely proportional” to one another. When I was teaching electronics technology & engineering in college, I was stunned to find how many of my students did not know what “inversely proportional” meant, so I had to take time explaining it.

    By the way, the speed that you travel and the time that it takes to get there are inversely proportional to one another. Sorry – I thought that this was common knowledge, but I had to explain it to my college students.

    If the electromagnetic radiation is passing though some other transparent or translucent material, then there is a slight adjustment that has to be made in the calculation of the wavelength and the speed of propagation. They both get smaller, but the frequency stays the same.

    Actually, our perception of color depends on the frequency and not really on the wavelength. Hence, color and wavelength are not really synonymous, but the adjustment is usually a small one.
    That leads us into Quantum Mechanics, but we don’t want to do that here!

  2. There was a fellow who went to the same high school and college with me, and he decided that FISHERIES would be an interesting course of study. That is in the College of Agriculture in some universities.
    Maybe fishing poles, fishing lines, nets, bait, how to catch fish?

    This fellow found out that in Fisheries, the students have to study some math, and LOTS of biology and chemistry, and some physics, before they can progress higher. Fisheries is all about growing healthy fish efficiently in lakes, ponds, and fish farms, as well as managing fish growth in the ocean. He found out the hard way the first semester during his freshman year when he had to take math, biology, and chemistry, and he ended up getting two Ds and an F.

    Soon, he decided to change his major, and some years later he graduated with a B.A. in JOURNALISM. Yikes!

    I was in another group from that same high school who earned our degrees in medicine (several doctors), engineering (more than one kind), geology, pharmacy, aeronautics, math education, etc.
    We put our math, physics, chemistry, and biology to work.
    Then the fellow with his B.S. in geology decided to study for his M.B.A., and he never did work as a geologist. He spent 20 years as an officer in the Air Force, working in management most of the time.

  3. I have noticed that nowadays lots of writers do not know what an appositive IS. It is pathetic.

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