ਜੀਵ ਵਿਗਿਆਨ ਵਿੱਚ ਪ੍ਰਾਣੀ ਜਾਂ ਜੀਵ (ਸਜੀਵ) ਕੋਈ ਵੀ ਜਿਊਂਦਾ ਪ੍ਰਬੰਧ ਹੁੰਦਾ ਹੈ ਭਾਵ ਜਿਸ ਵਿੱਚ ਪ੍ਰਾਣ ਹੋਣ, ਜਿਵੇਂ ਕਿ ਰੀੜ੍ਹਧਾਰੀ, ਕੀੜਾ, ਪੌਦਾ, ਬੈਕਟੀਰੀਆ ਆਦਿ। ਹਰੇਕ ਪ੍ਰਾਣੀ ਟੁੰਬ ਜਾਂ ਉਕਸਾਹਟ ਦਾ ਜੁਆਬ ਦੇਣ, ਮੁੜ-ਉਤਪਤੀ ਕਰਨ, ਵਿਕਾਸ ਅਤੇ ਵਾਧਾ ਕਰਨ ਅਤੇ ਸਵੈ-ਨਿਯਮਤ ਕਰਨ ਵਿੱਚ ਕੁਝ ਹੱਦ ਤੱਕ ਸਮਰੱਥ ਹੁੰਦਾ ਹੈ।

An organism is defined in a medical dictionary as any living thing that functions as an individual. Such a definition raises more problems than it solves, not least because the concept of an individual is also difficult. Many criteria, few of them widely accepted, have been proposed to define what is an organism. Among the commonest is that an organism has autonomous reproduction, growth, and metabolism. This would exclude viruses, despite that fact that they evolve like organisms. Other problematic cases include colonial organisms; a colony of eusocial insects is organised adaptively, and has germ-soma specialisation, with some insects reproducing, others not, like cells in an animal's body. The body of a siphonophore, a jelly-like marine animal, is composed of organism-like zooids, but the whole structure looks and functions much like an animal such as a jellyfish, the parts collaborating to provide the functions of the colonial organism.