As the generic corpus cease- lessly expands, genres (and the relationships be- tween them) change over time; the conventions of each genre shift, new genres and sub-genres emerge and others are 'discontinued' (though note that cer- tain genres seem particularly long-lasting).

How and why do genres change over time?

Influence of particular texts,  Genres can be heavily influenced and suddenly rekindle their popularity or change direction because of the impact of individual texts which come to be seen as genre defining.

How do film genres change over time?

Genres may change over time by adding or omitting elements. Some elements have been dominant as long as story telling has existed, others are adaptations to changing social and cultural conditions.