noun (n)

• the quality of being mentally slow and limited(noun.cognition)

  Synonym:
  dumbness, slow-wittedness
  

  source: wordnet30
• the spatial property of being crowded together(noun.attribute)

  Synonym:
  compactness, concentration, density, tightness
  Antonym:
  dispersion, distribution
  

  source: wordnet30
• the amount per unit size(noun.attribute)

  Synonym:
  density
  

  source: wordnet30
• The quality of being dense; density.(noun)

  source: webster1913