The definition does not include items which should be included.
- An apple is something which is red and round. (Golden Delicious apples are apples, however, they are not red (they are yellow). Thus they are not included in the definition, however, they should be.)
- A book is pornographic if and only if it contains pictures of naked people. (The books written by the Marquis de Sade do not contain pictures. However, they are widely regarded as pornographic. Thus, the definition is too narrow.
- Something is music if and only if it is played on a piano. (A drum solo cannot be played on a piano, yet it is still considered music.)