All of the provided options can assist readers in understanding and defining words to varying degrees. However, if you are looking for the choice that is most directly helpful in defining words, it would be:
C. Parts of speech.
Knowing the part of speech (e.g., noun, verb, adjective) provides context for how a word is used in a sentence, which is crucial for grasping its meaning.
That said, each element plays a role:
- A. Pronunciations help in understanding how to say the word correctly.
- B. Etymological patterns provide insight into the origin and historical development of the word, which can lend understanding to its current meaning.
- D. Stressed syllables aid in correct pronunciation, particularly in terms of word emphasis in spoken language.
Ultimately, for defining, parts of speech are the most integral.