From concentrate + -ation.

concentration is on the Academic Word List.
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Etymology change

Pronunciation change

Noun change

Singular
concentration

Plural
concentrations

  1. (countable & uncountable) A concentration is a large amount of something in one place or group.
    The oil-sands in Alberta, Canada, contain high concentrations of oil.
    The growing concentration of people in cities is causing new problems.
  2. (uncountable) Concentration is the ability to focus your attention on something.
    Runners mustn't worry or do anything else to break their concentration.
    A clean desk in a quiet place will help students improve concentration.
    The government's concentration should be on helping those in the greatest need.
  3. (chemistry) The amount of solute in a solution; the concentration of a solution is measured in parts per million (ppm)