The ohm is the unit of electrical resistance.

A conductor (wire, resistor, anything metal, carbon, semiconductor etc) has a resistance of 1 ohm when an applied voltage of 1 volt causes 1 amp to flow through the conductor.

If V is the voltage, R is the resistance in ohms and I is the current then Ohms law states:

I = V/R

or

R = V / I

i.e. The current flowing through a resistance equals the voltage divided by the resistance in ohms

The Greek letter omega is the symbol used for ohms

The symbol ? (Greek letter Omega) means 'Ohm'. It is a unit used to measure the electrical resistance of a conductor.

One ohm is defined as the amount of electrical resistance offered by a conductor when a current of one ampere flows through it under one volt of potential difference is applied across its ends.

Barriers electrical resistance is the ratio between the voltage of an electronic component (eg resistor) with electric current through it. Electrical resistance can be formulated as follows: R = V / I or where V is voltage and I is current. A unit for resistance is the Ohm (R)

...The SI unit for resistance is the volt per ampere.This combination occurs so often that a special name is given, the ohm.

i.e. 1 ohm=1 volt per ampere

=1V/A

The term ohm is a unit of electrical resistance. The term mho is a unit of electrical conductance.

1 ohm = 1/ 1 mho

It is a measure of resistance. An electrical current is being resisted, and the degree of resistance is measured in ohms.

...Ohm is a measure of resistance.

for more information refer the wikipedia

hope this will help you