'Lightbulb' and 'bulb' are largely interchangeable, though 'bulb' is slightly shorter and more common in instructions such as 'screw the bulb in clockwise'. 'Lamp' can mean either the lightbulb itself (in technical contexts like 'lamp wattage') or the entire fixture — a possible source of confusion. 'Globe' refers specifically to round, spherical lightbulbs (common in decorative fixtures). 'Tube light' or 'fluorescent tube' describes the long cylindrical shape, not a traditional lightbulb. Example: 'The globe in the dining room chandelier shattered,' vs. 'The tube light in the garage needs replacing.'
A compound noun formed from 'light' (from Old English 'leoht', meaning brightness or illumination) and 'bulb' (from Latin 'bulbus', meaning an onion-shaped root — the rounded glass shape reminded early inventors of an onion). The word 'lightbulb' came into everyday use in the late 19th century after Thomas Edison's practical electric lamp design became widespread.