1.defination--
osi model is a layered framework for design of network system that allows to communicate with all the computer system, and tcp/ip is a protocal suite that defines how data is exchanged across varoius computers over internet.
2.purpose---
purpose of osi model is to show that how to faclitate a communication between different computers without requring changes in the logic of h/w and s/w. whereas the purpose of tcp/ip is to connect multiple networks.
3.no of layers---
the osi model has 7 layers,whereas tcp/ip has 4 layers.
4.protocol/model ---
osi model is a model not a protocol .i.e first the model was designed and then protocol was designed,whereas tcp/ip model is reverse of the osi model. i.e. first protocal was designed and the model is use as a discripition of an existing protocol.

The major differences between the OSI and TCP/IP are:

# The application layer in TCP/IP handles the responsibilities of layers 5, 6 and 7 in the OSI model.

# The transport layer in TCP/IP does not always guarantee reliable delivery of packets at the transport layer, while the OSI model does. TCP/IP also offers an option called UDP that does not guarantee reliable packet delivery.