Difference between Psychology, Physiology and Phycology

I was looking for online books on Psychology and got few unfamiliar terms

Well I was familiar with the term Physiology but Psychology Phycology was totally new for me. On wiki I found the following definition

Phycology (from Greek φῦκος, phykos, "marijwana"; and -λογία, -logia) or algology (from Latin alga, also "seaweed"), a subdiscipline of botany, is the scientific study of algae.
Physiology (from Greek φύσις, physis, "nature, origin"; and -λογία, -logia, "study of") is the study of the mechanical, physical, and biochemical functions of living organisms. Physiology has traditionally been divided between plant physiology and animal and all living things physiology but the principles of physiology are universal, no matter what particular organism is being studied. For example, what is learned about the physiology of yeast cells may also apply to human cells that one may be studying.

Psychology (Greek: Ψυχολογία, lit. "study of the mind", from ψυχή psukhē "breath, spirit, soul"; and -λογία, -logia "study of"[1]) is an academic and applied discipline involving the systematic, and sometimes scientific, study of human or animal mental functions and behavior.

God save the medical student in their study. But there are lots of online medical books