Which of the following best characterizes an interjection?

An interjection is indeed best characterized as a minor part of speech that expresses strong emotions. This type of word is often spontaneous and conveys feelings such as surprise, joy, anger, or excitement. Examples include words like "wow!," "ouch!," and "yay!," which are typically used to express an immediate emotional reaction.

This categorization highlights the unique function of interjections, differing from other parts of speech that may serve grammatical purposes or convey more structured meanings. Interjections stand alone in their emotional expression, without serving as substantive elements in the sentence structure.

The other options do not accurately reflect the nature of interjections. For instance, interjections are defined by their emotional value rather than the absence of it, are not specifically formal terms used in academic writing, and they do not serve any connective function like conjunctions. This underlines the distinct role interjections play in language as expressions of emotion rather than structural components.