Question

Define mutual inductance of two coils and write its si unit

Answer 1

The property of the coils that enables it to oppose the changes in the current in another coil  is known as mutual inductance. It's SI unit is henry

Hope it helps!

Answer 2

mutual inductance of two coils is defined as the flux linked in secondary coil due to the unit current flowing in primary coil.
Its SI unit is Henry (H).