Hello, another definition of the verb 'contain' is 'be made up of (a number of things); consist of' and this would apply more to your first example, 'The list contains the groceries'. You are right in saying that the list does not contain any physical groceries, however, the list is made up of a number of grocery items or consists of a number of grocery items. This list will then be used to buy the physical items when shopping at the grocery store. In your second example, 'My idea is contained in the book', once again there are no physical properties in an idea. The definition you mentioned, 'have as contents, what is spoken or written about' would apply to this example. The 'idea' is written about or included in the book. The challenge with vocabulary is that a word may have multiple meanings or may suggest different things based on the context they are being used in. I hope this helps you! Eric.