title: CR4
text: # CR4
  
  CR4 may refer to:
  
  ## Science and technology
  
  * Complement receptor 4, a complement receptor in the immune system
  * CR4, a control register in the x86 CPU architecture
  * 100GBASE-CR4 and 40GBASE-CR4, in 100 Gigabit Ethernet and 40 Gigabit Ethernet
  
  ## Other uses
  
  * CR4, four-firm concentration ratio, a measure of market concentration in economics
  * CR4, a postcode district in the CR postcode area in England
  * Pasir Ris East MRT station (CR4), an upcoming MRT station on the Cross Island Line in Singapore
  