What is lighting fixturein construction?

They are the same thing. Luminaire is the formal term used in specifications, photometric data, and most fixture schedules (you will see luminaire schedule on the electrical sheets), while fixture is the everyday word in the field and in estimating. When a spec section references luminaires and the plans say fixtures, no scope difference is intended; the type tags tie the two together.

Each, by type tag. The estimator counts every Type A on the plans, then every Type B, and so on, keeping one line per type because each type has its own material and labor cost. Counts come off the lighting plans or the RCP, never both added together, and any quantity column printed on the fixture schedule gets treated as a cross-check, not a takeoff; the plans govern.

Mounting and access drive the labor side: lay-in grid is fastest, recessed cans in hard lid are slower, and anything suspended at height needs lifts and more crew time. On the material side, the driver and controls matter as much as the housing; dimming drivers, integral sensors, and emergency battery packs all add cost. Ceiling height alone can change labor noticeably, which is why the RCP belongs next to the lighting plan during takeoff.