A consonant cluster occurs when a group of consonants is not broken up by the presence of a vowel. These clusters must also represent more than one sound. Typical English consonant clusters include ‘spl’ and ‘str.’ The longest clusters include the ‘lfths’ part of "twelfths."
The English language is divided into vowels and consonants. Theoretically, there are 21 consonants and five vowels. Some letters, like Y, can function as both depending on the context. Many languages, especially Slavic ones, have fluid consonants like L and R that can function as vowels. Other languages like Japanese have few independent consonants — just N.
A digraph occurs when two letters form to make one sound. For example, ‘ch’ is a digraph. Other examples of digraphs in English include ‘ng,’ ‘sh’ and ‘wh.’ Digraphs can also be formed through two vowels like ‘oo,’ ‘ou’ and the Old English ‘ae.’ Some languages also combine three letters to form a single sound, known as a trigraph.
Hungarian uses the same letters as English, but derives different sounds. For example, a Hungarian digraph ‘sz’ is an English monograph ‘s,’ while a Hungarian ‘s’ is an English digraph, ‘sh.’ What appears to be a digraph in one language is a consonant cluster in another. The Hungarian word ‘esszeru’ is pronounced ‘esh-sze-ru.’
There is some disagreement between linguists over what constitutes a consonant cluster. Some believe that a consonant cluster must be held within one syllable so that the ‘mpl’ of complacent is not a consonant cluster. Other linguists believe that such clusters must be able to cross the syllable boundary.
Consonant clusters have reduced in numbers as English has developed. This often took the form of the final letter changing from a distinct sound to a silent presence used as a visual trick to separate one word from a similar-sounding one, leading to whole and hole, and plum and plumb. African-American and Caribbean English speakers have further reduced consonant clusters by dropping the last consonant entirely to change hand in to 'han,' and desk into 'des.'
Some languages have removed consonant clusters entirely. Italian, Portuguese and Catalan are three prime examples of consonant cluster reduction. This has led to Victoria becoming "Vittoria" in Italian. The word length did not change, but the "c" was dropped to shorten the sound.
Foreign language speakers from languages with few consonant clusters find it difficult to learn languages such as English and German. Spanish, Arabic and Japanese speakers find it particularly hard. It often takes such learners longer to get to grips with consonant clusters.
Japanese has borrowed 10,000 English and German words into its lexicon, but has had to find ways of dealing with consonant clusters. Some languages absorb words without changing them, but Japanese molds the words to fit its syllable-based language. The Japanese dealt with the consonant cluster by breaking it up so that symmetry became ‘shimetorii,’ example became ‘ekusampulu’ and spring became ‘supuringu.’