Definition of a Resistor:
A resistor is an electronic component designed to impede the flow of electric current in a circuit. It is a passive two-terminal device that converts electrical energy into heat energy. Resistors are widely used in various electronic devices and circuits to control the amount of current flowing through them.

Definition of a Rheostat:
A rheostat is a type of variable resistor that allows the user to adjust the resistance value manually. It consists of a resistive element and a sliding contact, which can be moved along the resistive element to change the resistance. By adjusting the position of the sliding contact, the resistance in the circuit can be increased or decreased, thus regulating the current flow.

Definition of Resistivity:
Resistivity, often denoted by the Greek letter rho (ρ), is a property of a material that quantifies its ability to resist the flow of electric current. It is a fundamental property used to characterize the electrical behavior of materials. Resistivity is measured in ohm-meters (Ω·m) and is dependent on the dimensions, shape, and composition of the material.

Resistor:
- A resistor is an electronic component used to control the flow of electric current.
- It is a passive device, meaning it does not require any external power source to function.
- Resistors are typically made of a material with high resistivity, such as carbon, metal, or metal oxide.
- The resistance of a resistor is determined by its physical dimensions, material properties, and temperature.
- Resistors are often color-coded to indicate their resistance value.

Rheostat:
- A rheostat is a variable resistor that allows manual adjustment of its resistance.
- It consists of a resistive element and a sliding contact that can be moved along the element.
- By changing the position of the sliding contact, the resistance in the circuit can be increased or decreased.
- Rheostats are commonly used in applications where precise control of current or voltage is required, such as dimmer switches or volume controls.
- Unlike fixed resistors, rheostats provide a variable resistance that can be adjusted according to the desired level.

Resistivity:
- Resistivity is a property of a material that determines its ability to resist the flow of electric current.
- It is an intrinsic property of a material and depends on factors such as its composition, temperature, and impurities.
- Resistivity is typically measured in ohm-meters (Ω·m) and is denoted by the Greek letter rho (ρ).
- Materials with high resistivity, such as ceramics or rubber, impede the flow of current more effectively than materials with low resistivity, such as metals.
- Resistivity is used to calculate the resistance of a conductor based on its dimensions and shape, using the formula R = ρ(L/A), where R is the resistance, ρ is the resistivity, L is the length of the conductor, and A is its cross-sectional area.

Resistor is is component that provide resistance to the flow of electric current
rheostat is the variable resistance provider component in the electric circuit
resistivity is the property of the material which provide resistance to flow of current