maturation

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun The process of becoming mature.
• noun 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.
• noun 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.

from The Century Dictionary.

• noun The process of ripening or coming to maturity; a bringing to maturity; hence, a carrying out; consummation.
• noun In medicine, a ripening or maturing, as of an abscess; formation of pus; suppuration.
• noun In cytology and embryology, the final stage in the development of the germcells (ovum and spermatozoön). This stage is characterized by certain changes in the chromosomes, especially a reduction in their number to one half of that of the chromosomes in the somatic or body cells.

from the GNU version of the Collaborative International Dictionary of English.

• noun The process of bringing, or of coming, to maturity; hence, specifically, the process of suppurating perfectly; the formation of pus or matter.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun The process of becoming mature
• noun biology The process of differentiation that produces the adult form of an organism

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun (biology) the process of an individual organism growing organically; a purely biological unfolding of events involved in an organism changing gradually from a simple to a more complex level
• noun coming to full development; becoming mature
• noun (medicine) the formation of morbific matter in an abscess or a vesicle and the discharge of pus