Noun extremum has 2 senses
  1. extreme point, extreme, extremum - the point located farthest from the middle of something
    --1 is a kind of extremity
    --1 has particulars: vertex, peak, apex, acme
  2. extremum, peak - the most extreme possible amount or value; "voltage peak"
    --2 is a kind of limit, limitation
    --2 has particulars: minimum, lower limit; maximum, upper limit