“Antonym of ‘phenomenon’” refers to a word that is the opposite of “phenomenon”.
The word “phenomenon” typically refers to an observable fact or occurrence. For example, “The aurora borealis is a natural phenomenon.”
It's a bit difficult to find a true antonym for “phenomenon” as it is a rather specific and somewhat neutral term. However, one could perhaps argue that “non-occurrence” or “absence” could be seen as a kind of opposite in a loose sense. When there is a phenomenon, there is something happening or being observed. In contrast, when there is a non-occurrence or absence, there is no such event or occurrence taking place. For instance, “The lack of any visible change is in stark contrast to the usual phenomena we observe.”
Another way to think about an “opposite” might be to consider something that is not an observable event. For example, “obscurity” or “invisibility” could be seen as contrasting with the visibility and noticeability of a phenomenon. For example, “The hidden process is the opposite of a prominent phenomenon.”
In conclusion, while there isn't a perfect antonym for “phenomenon”, words like “non-occurrence”, “absence”, “obscurity”, or “invisibility” can offer some contrast and be considered in a way as opposites in certain contexts.