The dynamic fields in a record become inapplicable when you change or remove the parent record or the related record, or when you update the dynamic field definition of the parent record.
For example, consider a record named Borges Penne related to another record named Grocery. The Grocery record contains Allergens and Ingredients as the dynamic field definitions. In the Borges Penne record, you can enter values for Allergens and Ingredients. If you remove the relationship between the Grocery and Borges Penne records, the Allergens and Ingredients fields in the Borges Penne record become inapplicable fields if they have values. You can remove inapplicable fields, from the Actions menu.