The laser acronym spells out Light Amplification by Stimulated Emission of Radiation, a description of how the device makes its narrow, bright beam. Scientists coined the term in the late 1950s, and the first working laser was built in 1960.
The word has become so common that most people write it in lowercase, "laser," and never think of the letters at all. It is one of the best known examples of an acronym that turned into an ordinary word, like scuba and radar.
Quick facts
Stands for
Light Amplification by Stimulated Emission of RadiationType
Acronym, now a regular nounHow to say it
LAY-zerFirst working device
1960Came after
Maser, the microwave versionSeen in
Barcode scanners, surgery, fiber optic lines, levels, pointersRelated terms
The laser acronym meaning, word by word
| Letter | Word | Plain meaning |
|---|---|---|
| L | Light | Visible light or nearby wavelengths such as infrared |
| A | Amplification | Making something stronger |
| S | Stimulated | Triggered on purpose |
| E | Emission | Giving off, sending out |
| R | Radiation | Energy traveling as waves, here meaning light |
Notice that the small words "by" and "of" are skipped, as is usual in acronyms. "Radiation" here does not mean anything nuclear. Physicists use it for any energy that travels as a wave, and light is one kind.
How a laser works in simple terms
Inside a laser is a material, called the gain medium, that can be a crystal, a gas, a dye or a tiny chip. Energy pumped into it lifts its atoms to an excited state. When a particle of light passes an excited atom, it can trigger that atom to release a second particle of light that matches the first exactly. That is the "stimulated emission" in the name.
Mirrors at each end bounce the light back and forth, so each pass triggers more matching light. One mirror lets a little light escape, and that escaping light is the beam. Because all of it shares the same color and moves in step, the beam stays narrow and bright over long distances, unlike the glow of a flashlight that spreads out.
Where the word came from
Before the laser came the maser, a device that did the same trick with microwaves. Its name swapped the L for M: Microwave Amplification by Stimulated Emission of Radiation. When researchers in the late 1950s worked out how to do it with light, "laser" followed the same pattern. The first working laser, using a ruby crystal, flashed in 1960. Within a few decades lasers moved from labs into stores, hospitals and homes.
What does laser stand for in everyday life?
Most people meet lasers without noticing:
- Checkout lanes: scanners read the bars on a product code.
- Internet lines: fiber optic cables carry data as laser pulses.
- Health care: eye surgery, skin treatments and some dental work.
- Building sites: laser levels throw a perfectly straight line on a wall.
- Classrooms: pointers during a slide show.
- Mapping and cars: LIDAR measures distance with laser pulses.
A warning label: "Caution: laser radiation. Do not stare into beam." Here "radiation" is the same word as in the acronym, and the label simply means the light can hurt your eyes.
Writing laser: capitals or lowercase?
Early papers wrote LASER in capitals. Today the lowercase word is standard in news, books and school writing, and it acts like any noun or adjective: a laser, two lasers, laser light. It has even become a verb in casual use, as in "the shop lasered our names onto the cutting board," though some editors avoid that. Use capitals only when you are pointing to the letters themselves, as this page does.
Laser is not to be confused with LED, light emitting diode. Both can be made from small chips, but an LED gives off a spread of light, while a laser gives a focused beam.
Look-alike acronyms that became words
Laser belongs to a small club of acronyms that people now use as ordinary words. Others include radar, scuba and sonar. To read how these differ from initialisms like USB, see what is an acronym, and browse more science and computing letters under tech acronyms.
Questions people ask
What does laser stand for?
Laser stands for Light Amplification by Stimulated Emission of Radiation. The name describes how the device multiplies matching light to form a beam.
Is laser an acronym?
Yes. It started as an acronym in capitals and is now written as a normal lowercase word. That kind of word is sometimes called an anacronym.
Does laser radiation mean it is radioactive?
No. In physics, radiation includes light itself. A laser gives off light, not nuclear radiation, though a strong beam can still harm the eyes or skin.
What is the difference between a laser and a maser?
A maser does the same thing with microwaves, which is where its M comes from. The maser came first, and the laser was named on the same pattern.
How do you pronounce laser?
Say it as one word, LAY-zer. Nobody reads it letter by letter.