Metaphors are indirect comparisons between two unlike subjects using "is" that transfers attributes between the subjects. There are many types of metaphors including dead metaphors whose metaphorical meaning is no longer understood, extended metaphors that use multiple comparisons, and conceptual metaphors that shape fundamental understandings. Idioms differ in that their meanings are not related to their individual words but are adopted phrases, though some idioms can also function metaphorically by creating comparisons.