1. Perfect Competition Large no of buyers & sellers Homogenous products
Free entry & exit
Perfect market knowledge
Indifference
Perfect mobility of factors
No Transport cost

2. Equilibrium in Short Run
Under identical cost
Under differential cost
Assumptions- 1)The firm is rational. 2) Product market 3) Factor market 4) Firm operates under U shape cost curve 5) Market mechanism exists. Excess profit , Normal profit, Sub-normal profits, Shut down point
Different perfect competing firms face any of the given situations. Excess profit, Normal profit, Loss but covers TVC & part of FC, Covers only TVC( Shut down point)

3. Equilibrium in Long run
Each firm adjusts its output by changing the scales of plant & hence the long run AC curve is disc shaped. Necessary condition – P=LMC=LMR=LAC=LAR.

4. Monopoly
One seller controlling the entire supply of the commodity for which there is no substitute at all. Very often found