Phrase is not linked to phrase set

What causes this issue?

The phrase you are currently working on has no connection to a phrase
set.

System Response

The system issues an error message and will not allow you to continue with this transaction until the error is resolved.

How to fix this error?

You should assign the phrase to a phrase set so you can use it for
characteristic value assignment.

Error message extract from SAP system. Copyright SAP SE.