solenoid – a wire wrapped into the shape of a coil that generates a strong magnetic field when current flows through it

(pronounced sol-uh-noid)

To remember the meaning of solenoid, use the following mnemonic:

The soldier got annoyed (solenoid) when he was wrapped in a coil of wire in a field of magnets (magnetic field)

A solenoid is a long coil of wire, typically cylindrical in shape, that produces a strong, uniform magnetic field when electric current flows through it, making it a type of electromagnet. The coil consists of many turns of wire wrapped closely together, and when current passes through these turns, each loop generates a magnetic field which combines with the adjacent loops to create a concentrated magnetic field inside the coil.

The magnetic field pattern of a solenoid is similar to that of a bar magnet, with magnetic field lines running parallel to the axis inside the coil and looping around the outside, creating a north pole at one end and a south pole. 

The strength of the magnetic field inside a solenoid can be increased by using more turns of wire, increasing the current flowing through the wire, or placing an iron core inside the coil, which becomes magnetised and significantly enhances the magnetic field strength. 

Solenoids have numerous practical applications, including electromagnets used in scrapyards to lift magnetic materials, electric bells and buzzers, where the solenoid attracts a metal striker, and circuit breakers that automatically disconnect circuits when excessive current flows. The ability to turn the magnetic field off and on by controlling an electric current makes them very useful.

If you want to know the difference between an electromagnet and a solenoid link here.