The term "after-parts" refers to the rear end or backside of an object or living being. The antonyms for this word aren't entirely straightforward, as there are different ways to approach this. The opposite of the after-part of something could be the front or top, depending on the object. For example, the front-end of a car is the antonym to the after-part. Another possible antonym could be "head", referring to the front or top of a living being. Alternatively, the terms "beginning" or "start" could also be seen as antonyms, as they refer to the opposite end of a process or journey.