child psychology vs psychology

child psychology and psychology both are nouns.

Word	Noun	Adjective	Verb	Adverb
child psychology	Yes	No	No	No
psychology	Yes	No	No	No

As nouns, psychology is a hypernym of child psychology; that is, psychology is a word with a broader meaning than child psychology:

child psychology: the branch of psychology that studies the social and mental development of children
psychology: the science of mental life

Other hypernyms of child psychology include psychological science.

child psychology (noun)	psychology (noun)
the branch of psychology that studies the social and mental development of children	the science of mental life