diencephalons

ˌdʌɪɛnˈsɛf(ə)lɒn
ˌdʌɪɛnˈkɛf(ə)lɒn

noun

the caudal (posterior) part of the forebrain, containing the epithalamus, thalamus, hypothalamus, and ventral thalamus and the third ventricle.