so·ci·o·bi·ol·o·gy 
(sō′sē-ō-bī-ŏlə-jē, -shē-)
(sō′sē-ō-bī-ŏlə-jē, -shē-)n.
The study of the biological determinants of social behavior, based on the theory that such behavior is often genetically transmitted and subject to evolutionary processes.
so′ci·o·bi′o·logi·cal (-bī′ə-lŏjĭ-kəl) adj.
so′ci·o·bi·olo·gist n.
- understeer
- understood
- understory
- understratum
- understudy
- undersubscribed
- undersupply
- undersurface
- undertake
- undertaker
- undertaking
- under the circumstances
- under the counter
- under-the-counter
- under the gun
- under the hammer
- under the influence
- under the knife
- under the rose
- under the skin
- under the sun
- under the table
- under-the-table
- under the weather
- under the wind