Definition: In relation to human development, the word "domain" refers to specific aspects of growth and change. Major domains of development include social-emotional, physical, language and cognitive. Kids often experience significant and obvious change in one domain at a time, so it may seem that a particular domain is the only one experiencing developmental change during a particular period of life. In fact, however, change typically is also occurring in the other domains but it's occurring gradually and less prominently.
For instance, tweens typically demonstrate significant developments in the social-emotional domain as peers become more central to their lives and they learn how to carry out long-term friendships. Parents typically notice major increases in social skills during this time. On the other hand, language development is less central during the tween years; the major, obvious increases in language development occurred earlier in life. Still, language development continues to occur during the tween years. For example, tweens are acquiring new vocabulary and enhancing their speed and comprehension when reading.
All in all, development in certain domains may seem more prominent during specific stages of life, yet kids virtually always experience some degree of change in all domains. Thus development is a multi-faceted process comprised of growth, regression and change in many different domains.
Berger, Kathleen. The Developing Person Through the Lifespan. 2008. 7th Edition. New York: Worth.