stem cell: stem cells are cells that are unspecialized but can become many different types of cells
differentiate: the process of unspecialized cells becoming specialized cells (National Institute of Health [NIH] & U.S. Department of Health and Human Services [DHHS], Stem cell basics, 2006)
embryo: the very early developing human
fetus: the human young in a womb in the later months of developing
in vitro: literally translated to "in glass" it means happening in an artificial, laboratory environment
multipotent: able to differentiate into many different specialized cell types (NIH & DHHS, Stem cell basics, 2006)
plasticity: the ability of adult stem cells from one tissue to differentiate into cell types different from those normal in that tissue (NIH & DHHS, Stem cell basics, 2006)
pluripotent: able to differentiate into almost all specialized cell types (NIH & DHHS, Stem cell basics, 2006)
progenitors: partially differentiated stem cells which have some characteristics of specialized cells and can differentiate into a variety of cell types, but not all types (Princeton University, 2005)
proliferation: the act of stem cells replicating without becoming differentiated
