A more thorough explanation:

An appurtenance is something that is considered an essential part of something else, even though it can technically be detached. When property is transferred, all appurtenances usually transfer with it. This is important to consider when there are liens on the property.

For example, a ship can still sail without radar systems, but if a radar system is installed, it would be considered an appurtenance to the ship. If the ship is seized due to a lien, the radar system would transfer with the ship. Other examples of appurtenances include swimming pools, water heaters, and kitchen cabinets. These are things that a person would expect to transfer when the property is sold.

Something can be appurtenant even if it is not attached to the primary property at the time of transfer. For instance, if someone buys propellers and tail shafts with the intention of installing them in a ship, they would still be considered appurtenant to the ship, even if they are not yet attached.

The term appurtenant also applies to appurtenant easements, which are easements that attach to land. These easements transfer with the attached property.

Overall, an appurtenance is something that is so essential to a property that it is considered a part of it, even if it can technically be detached. This is important to consider when transferring property or dealing with liens.