Led - LED

The word led (in lower case letters) is the past tense of the verb 'to lead'. There is a note about that at Lead - led.

In upper case, however, LED is a relatively new word, introduced in electronic engineering and such technologies. It is an acronym, standing for 'Light Emitting Diode: a form of transistor that responds to the passage of electric current by emitting light. Many of the little lights that show (or flash) green or red on computer equipment and other pieces of modern technology are made visible by the use of LEDs.