The ability of a given substance to emit radiation when heated is proportional to its ability to absorb radiation. A black body is a theoretical body with properties such that it absorbs all the radiant energy falling on it, reflecting and transmitting none, and emits radiation perfectly freely. 

1) In scientific parlance, any object made of some solid material; 

2) The human body.

Part of a building such as a wall (assembly), the glass of a window, a floor slab and its foundations, a roof/ceiling assembly.

The external building fabric, separating the interior from the exterior; ie the walls (including windows and external doors), the roof, and the floor. 

The constructional elements of a building - walls, windows, floors, roof. 

Insulation which resists conduction and convection of heat due to its non-conductive material and entrapped gas or air. Examples are fibreglass batts and blanket, cork, urea-formaldehyde and poly-styrene. Each type of bulk insulation has its advantages and its disadvantages; some may be flammable, or may emit toxic fumes if they catch fire.