reduce

Concise Oxford English Dictionary © 2008 Oxford University Press:
reduce/rɪˈdjuːs/

▶verb

• 1 make or become smaller or less in amount, degree, or size.

  ■ boil (a sauce or other liquid) so that it becomes thicker and more concentrated.

  ■ chiefly N. Amer. (of a person) lose weight.

  ■ Photography make (a negative or print) less dense.

• 2 (reduce someone/thing to) bring someone or something by force or necessity to (an undesirable state or action).

  ■ (reduce someone to) make someone helpless with (shock, anguish, or amusement).

• 3 (reduce something to) change something to (a simpler or more basic form).

  ■ convert a fraction to (the form with the lowest terms).

• 4 Chemistry cause to combine chemically with hydrogen.

  ■ undergo or cause to undergo a reaction in which electrons are gained from another substance or molecule.

  The opposite of oxidize.

• 5 restore (a dislocated body part) to its proper position.

• 6 archaic besiege and capture (a town or fortress).

– phrases
reduced circumstances poverty after relative prosperity.
reduce someone to the ranks demote a non-commissioned officer to an ordinary soldier.

– derivatives
reducer noun,
reducibility noun,
reducible adjective.

– origin ME (orig. ‘restore’, hence ‘bring to a different state’ and ‘bring to a simpler or lower state’): from L. reducere, from re- ‘back, again’ + ducere ‘bring, lead’.