What are the opposite words for byproduct?

Antonyms are words that have opposite meanings. In the case of the word "byproduct", which refers to something produced as a result of something else, the antonyms could be "primary", "main", "essential", or "core". These words suggest that something is not incidental or secondary, but rather fundamental or necessary. For example, the primary purpose of a factory might be to produce goods, while any waste produced would be considered a byproduct. Therefore, the antonyms for "byproduct" reflect the idea that something is significant in its own right, rather than simply a byproduct of some other activity.