Diminutive suffixes are a type of word ending used to indicate smallness or endearment. The three most common diminutive suffixes are 'ettes' (5 letters), 'ETS' (3 letters), and 'ules' (4 letters). These suffixes are often added to nouns, adjectives, and verbs to create a more affectionate or diminutive form of the word. For example, the word 'PUPPY' could be made diminutive by adding the suffix 'ettes' to become 'puppettes'.