An inactive string is a string which is part of your project and available to be leveraged from Translation Memory, but no longer appears in a translated file or website. How a string becomes inactive depends on your project type.
In an Application Resource Files or Business Documents projects, an in-progress or completed string becomes inactive if the string is removed or deleted in the original file, or if the original file itself is deleted.
In a GDN project, a string will become inactive if the string is not referred to by the GDN for an extended period of time.
By default, the list view will hide all inactive strings. However, you can show inactive strings by setting the list view filter to Inactive Only.
Inactive strings cannot be edited or translated, but they do still form a part of your translation memory, so poor translations in an inactive string can cause issues with future translations. If you wish to edit the translation for an inactive string, you need to reactivate it by clicking Reactivate or, for multiple strings, selecting Reactivate String from the Actions menu. This action can be performed by Account Owners and Project Managers only.