A word family is a group of words that share the same ending — the part linguists call the rime. Once a child can read cat, the ending -at transfers for free to hat, mat, bat, rat and fat. One decoding step unlocks five or more words.
This is why word families are the fastest confidence-builder in early reading: they turn "every word is a new problem" into "I already know this pattern".
1. Family race. Say "-at" and see how many words your child can produce in 30 seconds.
2. Swap the start. Write c-at → change one letter → h-at → m-at → b-at. Reading and spelling in one go.
3. Odd one out. cat, hat, mat, dog — which does not belong? Naming the rule cements it.
4. Rhyme time. "I'm thinking of a word that rhymes with cat and you wear it on your head." Kids love this one.