What do the words dad weight and dish have in common?

The Words "dad," "weight," and "dish" all contain a single vowel that is repeated. In "dad," the vowel "a" appears twice; in "weight," the vowel "e" appears twice; and in "dish," the vowel "i" appears once but is part of a phonetic structure that emphasizes the sound. Additionally, they are all common nouns referring to people or objects in everyday life.