Which word is the closest synonym for "silly" as related to "inept"?

The closest synonym for "silly" as it relates to "inept" is "foolish." The term "silly" often denotes a lack of seriousness or demonstrating a light-hearted ineptitude, which aligns closely with the meaning of "foolish." Both terms convey a sense of lacking prudence or common sense, indicating actions or attitudes that may not be taken seriously or are considered lacking in rational thought.

In contrast, the other options represent characteristics that do not align with the essence of being "silly" or "inept." "Wise" suggests sound judgment and intelligence, while "serious" implies gravity and earnestness, which are contrary to the light-hearted and impractical connotations of "silly." "Crafty," on the other hand, refers to skillful deceit or ingenuity, which does not connect with the meanings of either "silly" or "inept." Therefore, "foolish" stands out as the term that encapsulates the core idea of being not just silly but also lacking in capability or effectiveness.