Semantics are fascinating. There are times when they really aren't relevant, and it is only the basic message that counts; at other times, the choice of wording is critical. I often find it useful to bend language to my own nefarious ends, in which instance semantics are an important tool. A prime example of that is illustrating conceptual contrasts through creative semantic differentiation. This works best when I don't adhere to what is in the dictionary but apply my own nuances to definitions. Of course, that only succeeds when those nuances are elucidated.
So leave your dictionaries on the shelf (no Web sites, either), and remember that the definitions expressed here are those of “Final Mix” and not necessarily those of Electronic Musician, Funk & Wagnall's, or your high school English teacher.
For a start, consider the difference between “concern” and “worry.” To me, the difference lies essentially in whether there's anything to be done in the situation. Say, for example, that your band gets booked to play on a popular, nationally syndicated radio show. It's an important gig, and you are really concerned about doing well. This qualifies as concern, because the band can rehearse like demons to address it.
Now consider a different scenario, in which you are a studio owner. A band booked to play a radio show has decided that if the show goes well, there will be enough response to justify spending the money to come into your studio and record. But if they don't do well or don't get the response they're hoping for, they won't book studio time. Times are tight, and you're worried about whether the booking will come through. This constitutes worry, because there's nothing you can do to influence the outcome.
Worry, on the whole, is not very valuable in my view, and I try to avoid it. I don't always succeed, but that is how I see it.
Another interesting difference is between “competent” and “good.” This one is a little trickier. Basically, I view the words as different levels on a scale of excellence. Most of the time, competence is a component of goodness. It is not uncommon, however, to experience something that is competent but not good. There are always performers whose technique is impressive but who, somehow, just don't have anything interesting to say. I refer to this syndrome as “CBU”: Competent but Uninspired. A good performer elicits a desired response from the audience, usually through competence combined with inspiration.
One of the most fascinating semantic differences, however, occurs between “reason” and “excuse.” Here's a reason: a band member phones you saying, “I'm not going to make the rehearsal tonight because I have the flu, and I've had a fever of 102 all day and haven't left the bathroom in five hours.” There's an explanation and a justification. The situation is beyond the person's control and clearly renders him or her unable to attend and perform as needed.
Then you get another phone call from a different band member (this is apparently not a good night) who says, “I'm not going to make the rehearsal tonight because an old friend showed up out of the blue, and we drank and took narcotics all afternoon, and now I'm totally hung over and haven't left the bathroom for an hour.” Well, the person is clearly rendered unable to attend and perform as needed, but that's due to a reckless choice to deliberately surrender control. There's certainly a reason, but no justification in it. Excuses include reasons, but reasons are not always excuses.
Even the word “control” poses a semantic issue for me, as I think it is a misnomer when applied to people's lives. As another one of my famous (in some circles) “O-grown” proverbs says, “a person has control over nothing in his life; he just has varying degrees of influence.”
I find this sort of semantic game useful beyond helping to devise appropriate turns of phrase. I play it more as an analytical tool for gaining insight into situations and attitudes. Drawing semantic distinctions can simplify things a bit, though simplification carries its own dangers. Alas, I am out of space and must wait for another time to discuss the difference between “simple” and “simplistic.”