Whenever I have seen the word “lamp” used in the context of lighting, I have often seen the word used in 2 different contexts. In one definition, I have seen the word “lamp” being used to refer to an entire light fixture such as in a “hanging lamp” or a “table lamp”. In another definition, I have seen the word “lamp” being used to define only the light source itself as in a “mercury vapor lamp” or a “fluorescent lamp”. Why is it that the word “lamp” in the context of lighting refers to an individual light emitting source or an entire light fixture containing the light emitting source?

In some cases, I sometimes feel like I end up confusing people whenever I say something like “This table lamp is using a fluorescent lamp”.

I generally use the word "lamp" to refer to a light source or "bulb" (which I hate by the way). When referring to a light fixture, I generally use the word "Luminaire" (generally for streetlights) or fixture.