On the flip side, the wonderful thing about these words being so common is that children learn them easily with repetition because they are usually words that they already have in their everyday vocabulary. Can you illustrate 'is' or 'it?' Me neither. They are often also difficult to illustrate, so children can't use illustrations in picture books to make a deeper connection to these words. But many of the words also defy standard phonetic conventions, meaning they are impossible to sound out. You might think that these words are so common that kids would just learn them organically through reading and other everyday print. Some of the words cannot be decoded using conventional strategies so memorizing them until they are known by sight is beneficial. They are a list of 220 words that are used so often in print that together they make up an estimated 75% of all words used in books. Edward William Dolch first compiled the full list and broke it down into five levels for children to learn by sight. Just to confuse you, when you see lists of sight words what you are usually seeing are lists of high frequency words or Dolch Words. That's not usually how the term is used, though. His sight words are the words that he can already recognize by sight without using any specific strategies.