A project tag can be useful across photographs taken on different days, but an accidental assignment should not require deleting the tag from the entire collection. First decide whether you are correcting selected media or changing the library’s keyword vocabulary.

Write down the intended spelling of the keyword and select a small known group. Keep one correctly tagged photograph outside that selection as a comparison. For example, two photographs may have received a workshop label accidentally while a third genuinely belongs to that workshop.

In Photos on Mac, select the intended items and use the Info window’s keyword field to add or remove a keyword. Window, Keyword Manager also applies keywords to selected photographs; clicking an assigned keyword again removes it from those photographs. Edit Keywords manages the vocabulary, and its Remove button deletes the selected keyword from all your photographs.

Keyword Manager also supports renaming a keyword and placing frequently used keywords in Quick Group. Those quick keywords become available through the filter menu. Keep the initial correction focused on the selection before making a broader vocabulary change.

Prove the scope with two examples

Remove the mistaken keyword from the small selected group. Reopen one of those photographs and inspect its keywords. Then open the correctly tagged photograph that was left outside the selection and confirm that the keyword remains there.

If your broader problem is inconsistent spelling, inventory the existing terms before changing them. Similar labels can have different meanings: a project name, a location and a status should not be combined merely because they often appear together.

Agree on a compact vocabulary that describes the actual retrieval task. A label should help answer a question such as which photographs document a particular installation, rather than become another vague version of Favourite.

Check retrieval after cleanup

Search for the accepted keyword and inspect a known included photograph and one that should now be excluded. Review unexpected results individually; clearing a result by deleting the photo would change the media collection rather than repair its label.

Keep a short explanation of the vocabulary with the project’s working notes, particularly if several people maintain the library. For future imports, assign a small batch first and repeat the included/excluded check. The goal is reliable retrieval with controlled assignment scope, while preserving photographs whose tags need correction.

Reference: Apple: Photos keywords and Keyword Manager.