What is the difference between mechanical, civil and electrical engineering?

Mechanical Engineering

This has to do with the design of any mechanical system and the assembly of different mechanisms to form a machine.

This can be combined with other elements, such as the study and effect of heat in motion (Thermodynamics), the flow and application of compressible and incompressible fluid (Fluid Mechanism), mechanical design and computer/electronics engineering with the application of automatic control. (Mechatronics) etc.

Electrical Engineering

Sometimes referred to as electrical and electronic engineering, is a field of engineering that deals with the study and application of electricity, electronics and electromagnetism.

Electrical engineering may or may not include electronics engineering. Electrical engineering deals with the problems associated with large-scale electrical systems such as power transmission and motor control, whereas electronic engineering deals with the study of small-scale electronic systems including computers and integrated circuits.

Alternatively, electrical engineers are usually concerned with using electricity to transmit energy, while electronic engineers are concerned with using electricity to transmit information.

Civil engineering

This is the engineering discipline that deals with the design, construction and maintenance of the physical and naturally built environment, including works such as bridges, canals, dams, road and buildings. It is traditionally broken into several sub-disciplines including environmental engineering, geotechnical engineering, construction engineering, coastal engineering, transportation engineering, water resources engineering, structural engineering, material engineering and surveying.

Civil engineering takes place on all levels: in the public sector from municipal through to federal levels, and in the private sector from individual homeowners through to international companies.

— Martin, recent mechanical engineering graduate