Origin: Germanic Old English prefix
Overlay has 7 different meanings across 2 categories:
protective covering consisting, for example, of a layer of boards applied to the studs and joists of a building to strengthen it and serve as a foundation for a weatherproof exterior
"The construction crew installed an overlay of plywood sheets over the old framing to reinforce the house before adding the new siding."
a layer of decorative material (such as gold leaf or wood veneer) applied over a surface
"The antique table was restored by carefully overlaying its worn legs with rich mahogany veneer."
A piece of paper pasted upon the tympan sheet to improve the impression by making it stronger at a particular place.
"The printer carefully placed an overlay on the tympan sheet to reinforce the area where the type would strike hardest during printing."
In plain English: An overlay is something placed on top of another thing to cover it up or add extra features without changing what's underneath.
"The old photo is visible through the semi-transparent overlay on top of the new picture."
To lay, spread, or apply something over or across; cover.
"The ancient map was carefully removed to reveal the newer overlay from 1920."
simple past tense of overlie
In plain English: To overlay something means to put it on top of another thing so that you can see both at once.
"The digital artist used an overlay to combine two different photos into one image."
Usage: Use overlay as a verb when describing one layer being placed directly on top of another surface, such as digital graphics or physical materials. Avoid confusing this with "underlay," which refers to placing an item beneath the main object rather than covering it.
The word overlay comes from Old English, originally meaning to lay something over another. It is formed by combining the prefix over- with the verb lay.