(physics, chemistry) A technique used to purify a metal, semiconductor or other solid in which a heating system slowly causes a series of molten zones to traverse the solid, leaving purer material behind it.

The region, between the Tropic of Cancer and the Tropic of Capricorn, characterised by a hot and humid climate; the tropics.

(finance) A bond (e.g., corporate debenture or government debt) that has no coupon (i.e., pays no interest), during the life of the issue. Such a bond is initially sold at a discount to its face value. The rate of return to the holder is derived from the gradual appreciation as the security moves toward maturity.

(geography) The part of the Earth between the geographical South Pole and the Antarctic Circle.

(firearms) The adjustment of a sight, exactly parallel to the axis of the bore of the gun to which it is attached.

(biology) an environment that allows the development of adaptive radiation

(cycling) A designated place along the course of a bicycle race where it is permitted for the riders to receive food and energy drinks from their team support personnel.

Any large portion of the Earth's land area which has a generally uniform climate and soil and therefore a high degree of uniformity in the composition of species; a number of different classifications have been proposed by different people.

(oceanography) That part of the deep body of an ocean or lake that receives insufficient sunlight for photosynthesis to be possible.

The part of the near-surface body of an ocean or lake that receives enough sunlight for photosynthesis to be possible.