1. A branch of biology that deals with the functions and activities of life or of living matter (as organs, tissues, or cells) and of the physical and chemical phenomena involved. (wiktionary.org)
2. Branch of biology that deals the study of the functioning of living organisms and the organs and parts of living organisms.
3. The scientific study of function in living systems. This includes how organisms, organ systems, organs, cells, and bio-molecules carry out the chemical or physical functions that exist in a living system. (wikipedia.com)
4. The Biological Science concerned with the Life-supporting properties, functions, and processes of living organisms or their parts. (online-medical-dictionary.com)
Word origin: From Ancient Greek φύσις (physis), meaning nature, origin, and –λογία (–logia), meaning study of