- 1. The compactness of a substance; the ratio of mass to unit volume, usually expressed as g/cm3 (kg/m3 in the SI system). 2. The quantity of electricity on a given surface or in a given time per unit of volume. 3. In radiological physics, the opacity to light of an exposed radiographic or photographic film; the darker the film, the greater the measured d.. 4. In clinical radiology, a less exposed area on a film, corresponding to a region of greater x-ray attenuation (radiopacity) in the subject; the more light transmitted by the film, the greater the d. of the subject; this is not actually the opposite of the prior definition, since one concerns film d. and the other subject d.. [L. densitas, fr. densus, thick]- bone d. quantitative measurement of the mineral content of bone, used as an indicator of the structural strength of the bone and as a screen for osteoporosis- flux d. 1. SYN: flux (4). 2. either particle flux d., the particle fluence rate, or energy flux d., the energy fluence rate of intensity. Cf.:fluence.- photon d. the number of counted events recorded in scintigraphy per square centimeter or per square inch of imaged area. SYN: count d..- vapor d. the mass per unit volume of a vapor; since the vapor d. changes with temperature and pressure, it is commonly expressed as a specific gravity, i.e., the weight of the vapor divided by the weight of an equal volume of a reference gas ( e.g., oxygen or hydrogen) at the same temperature and pressure.
* * *1) the quantity per unit volume, unit area, or unit length: asa) the mass of a substance per unit volumeb) the distribution of a quantity (as mass, electricity, or energy) per unit usu. of spacec) the average number of individuals or units per space unit <a population \density of 500 per square mile>2 a) the degree of opacity of a translucent mediumb) ABSORBANCE
* * *den·si·ty (denґsĭ-te) [L. densus dense] 1. the quality of being compact or dense. 2. quantity per unit space, e.g., the mass of matter per unit volume. Symbol ρ or d>. 3. the degree of darkening of exposed and processed photographic or x-ray film, expressed as the logarithm of the opacity of a given area of the film.
Medical dictionary. 2011.