1. Lacks a scientific precision in its definition
2. They developed in an informal way
3. Everyone (critics, producers, audiences, actors) have contributed to the formation of genres and to the shared sense that some films may relate to others
4. Genres change over time (directors and actors may add a twist to their work (in form or style) that adds to a different viewing of the genre). This constant change makes it difficult to define the boundaries

5. Genres social role can also change over time and challenged (example Lars Von Trier’s take on the musical with his film about death penalty “Dancer in the Dark”, questions the whole idea of musicals as escapists forms of entertainment)
6. Genres are easier to recognize than to define (as definitions are not set on stone)
7. Patterns in filmmaking appear quite regularly and these can create new genres or sub genres.
8. Genres can mix between themselves – adding to the challenge of their definition.
9. Audiences change and so does the genre (changes to fit the needs and the desires of the audiences)
10. The existence of genres allows to communicate to the viewer information about what they are about to see, hence simplifying or adding complexity to their movie watching experience
11. Most film genres and subgenres became established after one film was popular and then imitated.
12. New genres and subgenres are also established this way but they usually trace back influences. (for example “gross out” movies like “There is Something About Mary” are influenced by movies like “Porky’s“)
13. They do not remain successful for a long time – they have cycles. These cycles occur when a successful movie makes bursts of imitations. However action and horror movies have always been popular among audicences.
14. Genres are mixed by cross cultural references (for example the case of Sergio Leone’s “spaghetti westerns” and Hollywood’s action movies taking from Hong Kong movies)
15. Genres are bound to cultural factors – there are genres that are typical to a society (Colombians for example, love funny films that make reference to our own customs “costumbristas”)
16. Social change also affects the development of genres, hence genres can dwell and reflect upon social attitudes (example – “Planet of the Apes“, a Sci- Fi that deals with racism, fear of “otherness”, ‘specisim’)
17. Society can also affect the content of a movie and as such of the genre (take the new genre of “social conscious movies like “Blood Diamond” and “Hotel Rwanda” that have sprouted recently)