A word family is a group of words within which they share a common characteristic, pattern, or meaning. They usually share a common base or stem and have different prefixes and suffixes. This is a great way to think about or hear patterns of letters in words. The more word families you practice, the smarter your preschooler will become.
Grouping words into word families helps improve the predictability of letter pronunciation. The sounds that letters make depend on the other letters around them. For example, come up with many different ways to pronounce "a" based on words (eg map, cake, boat, head, said, salt, eat). Letters that rhyme in a word family form a stable unit that sounds the same in most words in which it occurs. This increases the likelihood that your child will read the letters correctly.
Teaching word families to your child can form a useful part of helping your child learn to read. A knowledge of word families helps your child to recognize unfamiliar words quickly and so builds their confidence during the difficult early reading stages. Teaching word families is an integral part of teaching reading using analytic phonics.