Which diacritical mark indicates a long vowel sound in a word?

The macron is the diacritical mark used to indicate that a vowel is pronounced as a long sound. It is typically represented as a horizontal line placed above the vowel. For example, in the word "ā," the macron signifies that the vowel "a" is elongated, altering the pronunciation from a short to a long vowel sound.

In teaching phonetics and the structure of language, understanding how diacritical marks function is crucial for effective communication about pronunciation. The macron helps distinguish the nuances of vowel sounds, which can be particularly important in language education contexts, such as Multi-Sensory Structured Language Education, where precise pronunciation aids in literacy development.

While other diacritical marks serve different purposes—such as indicating short vowel sounds or modifying pronunciation—the macron specifically denotes the lengthening of vowels, making it the correct choice in this context.