quaternary

Adjective

• coming next after the third and just before the fifth in position or time or degree or magnitude
  • the quaternary period of geologic time extends from the end of the tertiary period to the present
    

• consisting of or especially arranged in sets of four
  • quaternate leaves
    
  • a quaternary compound
    

Noun

• the cardinal number that is the sum of three and one

• last 2 million years

Related words

• Synonyms: 
  fourth , 4th , quaternate , Quaternary , Quaternary period , Age of Man