(~s)
1.
A ~ is a gradual development from one state to another.
Both drugs slow the ~ of HIV, but neither cures the disease...
= development
N-COUNT: usu sing, usu with supp
2.
A ~ of things is a number of things which come one after the other. (FORMAL)
...a ~ of habitats from dry meadows through marshes to open water.
N-COUNT: N of n