Epenthesis is the addition of a vowel or consonant sound to a word. This is applied differently to different languages, and works in various ways according to the needs of a set of speakers. The word comes from the Greek, where it could be translated into English as, "put into."
In many cases, epenthesis happens because speakers find it hard to pronounce vowel or consonant clusters, or sets of combined vowels and consonants, that are next to each other in words. Experts sometimes describe these ways of speaking as "child-like," where a given dialect inserts the sounds to make speech easier. The use of epenthesis in dialect is a major part of understanding how this phenomenon happens; speakers frequently add sounds into words in ways that are not technically correct, but become common usage over time, at least in specific language communities. The use of these extra sounds can also enhance a poetic meter.
One common example of epenthesis in English helps to describe how this process works. English speakers may use a "stopping" consonant as a kind of accent, in ways that are entirely superfluous. For example, inserting a "p" sound into a word like "hamster" or even a word like "teamster" gives the word a slightly different sound, but does not change its meaning or add substance.
In other cases, individuals insert vowel sounds to break up consonant clusters. One common tool in multiple languages is the use of what linguistic experts describe as a schwah. The schwah is a sort of ambiguous sound that resembles a diminished form of several vowel sounds in English, such as the "e" in roses, or the "u" in cup. It is often inserted into a particular place in a sentence, producing a distinctly different sound that may lead to its adoption as common usage.
Language experts formally refer to added consonant sounds as excrescence. Added vowel sounds are commonly called anaptyxis. Linguists and others observe the uses of these conventions at the beginnings, in the middles, and at the ends of words to understand how and why they are applied. Epenthesis is a good example of the ways that language is dynamic and continually changing. It also illustrates how dialect or informal language may differ from standard technically correct versions of that language, for example, how a broadcaster or communications professional may speak differently than a speaker of a particular regional or ethnic dialect.