1. definition
   1. of one good with respect to another
   2. measures nature and degree of the relationship
   3. between
      1. changes in the relationship
      2. quantity demanded
   4. in price of the second good
2. Results
   1. Elastic
   2. Inelastic
   3. Unit
3. Degree of relationahip
   1. The nature of the relationship is revealed by the Sign
   2. 0
      1. perfectly inelastic
   3. <1
      1. inelastic
         1. Change in demand is less then change in price
   4. 1
      1. unit elastic
         1. giffen good
            1. change in demand = change in price
         2. normal good
            1. luxury
   5. >1
      1. elastic
         1. change in demand is greater then change in price
   6. ∞
      1. perfectly elastic
4. Significance
   1. positive result
      1. substitutes
         1. inelastic
            1. distant
         2. elastic
            1. close
   2. Negitive
      1. complementary
         1. elastic
            1. weak
            2. close
5. Topic
   1. P1b
      1. original price of P
   2. P2b
      1. New price of P
   3. Q1a
      1. Original quantity of a
   4. Q2 a
      1. New quantity of a