Clusters of either consonants or vowels add to the challenge of beginning reading. Sometimes the clustered letters each make a sound, in which case early readers can apply phonetic decoding strategies to read them. However, other combinations make new or unexpected sounds that must be actively taught separately. Many reading specialists recommend that these more complicated sound patterns be taught after children demonstrate solid phonetic decoding skills.

Consonant Digraphs

Consonant digraphs are clusters of consonants pronounced as a single sound. There are seven basic consonant digraphs; ch, ck, th, sh, ph, ng, wh. However, "ch" has three pronunciations, "ch" as in chin, "k" as in chorus, and "sh" as in chute, and "th" is pronounced with active voicing as in "the" or without as in "thank." These discrepancies are often challenging for early readers, especially if they are also English language learners, because the sounds often resemble other letters. For example, "ph" combines to sound like "f." Three additional digraphs occur regularly in English, "wr," "gn" and "kn." These are referred to as "ghost digraphs because the initial letter used to make a sound but no longer does.

Consonant Blends

Blends are consonant pairs in which each consonant makes its own sound. For example, if you listen carefully, you can hear the "b" and the "l" in "blue." There are many blends in the English language. They are most often categorized into r-blends, such as "br" and "cr", s-blends, such as "sc" and "sk" and l-blends, such as "bl" and "cl." Blends are not usually a significant challenge for beginning readers. Reading blends uses a decoding strategy called blending that students are already using.

Vowel Digraphs

Vowel digraphs are pairs of vowels that make one sound. The first ones taught are usually those in which the initial vowel makes its long sound and the second is silent. For example, "e" is short when it's by itself in "men" and long when it's combined with "a" in "mean." The vowel digraph rule is frequently taught in schools with the saying "when two vowels go a walking, the first one does the talking." However, as with consonant digraphs, there are exceptions. For example, the "oo" in "book" is not pronounced "oh." Despite this, vowel digraphs are usually less challenging for beginning readers than consonant digraphs.


Diphthongs are the vowel version of blends. Rather than following the simple digraph rule, certain pairs of vowels such as "oy" in "toy" act like a blend and both sounds are pronounced. If "toy" followed the digraph rule, it would be pronounced "toe." As with consonant clusters, diphthongs can pose a significant challenge to rule-oriented beginning readers.