Receptor (noun)

1. A protein or cell surface molecule that binds to specific ligand molecules.
2. A site on a cell or organ that can be stimulated by a specific chemical or physical agent.
3. A protein or complex of proteins that receives chemical signals from outside a cell and transduces them into intracellular signals.

Origin:

The word "receptor" comes from the latin word "receptus" which means "to take back" or "to receive" and the suffix "-or" which denotes a person or thing that performs a certain action. this word came into use in the late 19th century in the field of biology and pharmacology to describe a protein or cell surface molecule that binds to specific ligand molecules.

Examples:

1. The drug binds to the receptor on the cell surface.
2. The hormone binds to its receptor on the cell membrane.
3. Receptors in the nose detect different odors.
4. Neurotransmitters bind to receptors in the brain.
5. The receptor is a protein that spans the cell membrane.