Any light source on set — from 1K Fresnel to LED panel. Catch-all term when precision doesn't matter.
On set, we say "lamp" when we mean a light source—whether it's a Fresnel, a softbox, an LED panel, or a reflector. The term is practically a universal key. The gaffer asks, "Where should we place the lamp?" The grip replies with the name of the actual fixture. "Lamp" is the quick word that works when there's no time for precision. It's also the term producers use when they don't know what a Par64 is—and nobody corrects them because everyone understands what is meant.
In practice, we distinguish between lamps based on their function: the key lamp illuminates the face, the fill lamp opens up the shadows, the back lamp separates the character from the background. A "hard lamp" casts sharp shadows—Fresnel, Par, Spot. A "soft lamp" diffuses light broadly—softbox, China ball, LED panels. The difference determines the entire mood of a scene. A 1K Fresnel creates drama, an LED panel creates objectivity. Both are "lamps," but their quality is completely different.
In modern productions, LED lamps have dominated the set—they save electricity, heat, and batteries. Previously, the question was: "How many watts of lamp do you need?" Today it's more like: "What's the color temperature?" and "How quickly does it dim?" The old tungsten lamp was constant, hard to dim, but its light was incomparably warm. LED lamps are flexible, precise, but only in the last ten years have they become truly cinematic. A good LED lamp today costs more than an old 5K HMI.
Practically speaking: When the DP says, "Put a lamp top left," he means: "Find a suitable light source, place it where it works." This could be a 300W LED, a softbox with Par lights, or even a window with a bounce board. The lamp is the tool, not the solution. The solution is light—and for that, you often need several lamps working together.