Photoluminescent

I was away for the weekend visiting family (where I got some good background information from some relatives on Armenian, which I'm starting to study on my own). On the plane there, the flight attendant was doing the kabuki dance titled "In The Event of an Emergency...", during which she mentioned that two strips on the floor of the aisle would light up so that we could find our way. She described these strips as photoluminescent.

If you'll forgive a moment of prescriptivism, that word bugs me, for two reasons. First, it's a Greek-Latin hybrid compound, although that isn't a terrible sin if you need to make a new distinction in meaning (e.g hypersonic for "much faster than sound" because supersonic was already taken). But it wasn't needed in this case, which brings us to the second reason it bugs me: the compound is completely redundant. Photo + luminescent means roughly "lit up with light". Luminescent (or even luminous) wasn't good enough? If you're going to add an extra morpheme, at least give me some extra information―maybe they're electroluminescent or bioluminescent?

Photoluminescent gets 20,700 ghits, though. Sigh.

UPDATE: As Rachel points out in a comment below, photoluminescent is actually a technical term for that green glow-in-the-dark stuff. That'll teach me to search in only two dictionaries before posting. I still wish they'd coined a better term for it. Luminoretentive? Photohysteretic?

Comments

[Rachel]

If you look it up, you'll see that "photoluminescent" isn't redundant at all. It means that something gives off light after having absorbed energy from light. Photons hit the material and excite the electrons (make them jump to higher energy levels). Then the electrons fall back down to lower energy levels, emitting photons.

Basically, this is your glow-in-the-dark whatever. You have to expose it to light before you take it in the dark and watch it glow.

Now, whether the stewardess used the word properly, that's another matter. Were the strips glow-in-the-dark?

[NW]

It's some kind of shift in the affix. Originally _photo-_ meant 'light', and was used to form compounds in the semantic domain of light. But numerous of these words now have their own proprietary domains, such as photography, photon, and photoelectric, and need to generate a prefix from some of their segments: so you get polysemic _photo-_ 'of or pertaining to photography' etc.

[Mike]

And we needed "hypersonic" because "supersupersonic" is a little strange. (Hypersonic is the range of spped beyond supersonic.)

The old radium-dial luminous watch faces were "luminescent"; they glowed without having to be "charged" by light.

Then there's phosphorescence.......

[The Gray Monk]

This stuff is widely used in fire safety as an alternative means for lighting up a means of egress, and it has the advantage of not needing wiring or light bulbs - just expose it to light and it charges up. Even artificial light will do. The downside is it will only give off very good light for about 20 minutes and then starts to fade out.

[Keith Ivey]

As Rachel says, the "photo-" prefix indicates the source of the energy for the luminescence. It's photoluminescence (luminescence powered by exposure to light), as opposed to chemiluminescence (from a chemical reaction), electroluminescence (from electricity), triboluminescence (from mechanical action), thermoluminescence (from heat), radioluminescence (from radioactivity), or something else.

http://www.uvminerals.org/luminese.htm

[includedmiddle]

Personally, I don't think photoluminescent is as bad as bioorganic. Although bioorganic at least has the decency to be all Greek and to stay out of the OED (for now at least).