Aftermath is defined as follows in the Oxford dictionary:
aftermath NOUN 1The consequences or after-effects of a significant unpleasant event.
Does it mean we can use it as the replacement of "after-effect"? For example, if my sentence is as follows:
The after-effects of the world war will be dreadful for the entire world.
Can I write it as follows:
The aftermath of the world war will be dreadful for the entire world.
I checked the example sentences given on the Oxford page. All these examples used the following phrase: "In the aftermath of". But if "aftermath" is used in such a way then the following definition from Cambridge looks more precise:
aftermath Noun the period that follows an unpleasant event or accident, and the effects that it causes: