In the previous chapter we already met various types of evolutions, including stationary and periodic ones. In the present chapter we investigate these evolutions more in detail and we also consider more general types. Here qualitative properties are our main interest. The precise meaning of ‘qualitative’ in general is hard to give; to some extent it is the contrary or opposite of ‘quantitative’. Roughly one could say that qualitative properties can be described in words (or integers), whereas quantitative properties usually are described in terms of (real) numbers.