Which aspect of a word is defined as the initial sound unit of the word?

• A. Rime
• B. Phoneme
• C. Onset
• D. Syllable

Answer: (C)

The initial sound unit of a word is known as the onset. The onset refers specifically to the consonant sounds that occur at the beginning of a syllable before the vowel. For instance, in the word "stop," the onset is "st." Understanding onsets is crucial in phonics instruction, as it helps students analyze and manipulate sounds within words, which is an essential skill for developing reading abilities.

In contrast, the rime refers to the part of the syllable that includes the vowel and any following consonant sounds, while a phoneme is the smallest unit of sound in a word, which can include both onsets and other sounds. A syllable represents a single unit of pronunciation that usually contains a vowel sound and can include an onset but is not specifically focused on just the initial sound. Thus, the definition of onset as the initial sound unit is clear and properly encapsulated in the correct choice.