A major or minor change in the design of an item, effected in order to correct a deficiency, to facilitate production, or to improve operational effectiveness.

Treatment of molten aluminum alloys containing 8-13% silicon with small amounts of a sodium fluoride or sodium chloride mixture; improves mechanical properties.

In nucleic acid metabolism, any changes made to deoxyribonucleic acid or ribonucleic acid after their original incorporation into a polynucleotide chain.

Any change brought about by external or internal factors.