1. The process of becoming mature.
2. Biology.
   1. The processes by which gametes are formed, including the reduction of chromosomes in a germ cell from the diploid number to the haploid number by meiosis.
   2. The final differentiation processes in biological systems, such as the final ripening of a seed or the attainment of full functional capacity by a cell, a tissue, or an organ.

The American Heritage® Dictionary of the English Language, Fourth Edition Copyright © 2007, 2000 by Houghton Mifflin Company. Updated in 2009. Published by Houghton Mifflin Company. All rights reserved.