A consonant is a sound in spoken language that is characterized by a constriction or closure at one or more points along the vocal tract, such as the lips, tongue and teeth. The word "consonant" also refers to each letter that denotes this type of sound. This term comes from a Latin word and means "sounding together" or "sounding with" — the idea being that consonants generally don't sound on their own but occur only with a nearby vowel. For instance, consonants typically cannot form words by themselves, although some might act as vowels in certain words. The Latin meaning of this term, however, does not reflect a modern linguistic understanding, which defines them in terms of vocal tract constrictions.
In the English alphabet, the 21 letters that typically denote consonant sounds are B, C, D, F, G, H, J, K, L, M, N, P, Q, R, S, T, V, W, X, Y and Z. The letter Y also can act as a vowel in words such as "myth" and "try." In two English words, the letter W also acts as a vowel: "cwm" and "crwth," with the sound being a long "u" sound. When a consonant letter acts as both a vowel and consonant in a word and is its own syllable, such as in the word "prism," it is called a sonorant. Some words that represent sounds also can consist entirely of consonants, such as "shh" and "brr."
Written English has fewer consonant letters than spoken English has consonant sounds — there are 24 common consonant sounds in English — so some letters represent more than one consonant sound. Letter pairs such as "sh," "th" and "ng" are used to represent some sounds. Some letters and letter combinations have different pronunciations in different words, such as the heavier "th" sound in "this," compared with the softer "th" sound in "thing." Since the number of consonant sounds in all the languages in the world is greater than the number of consonant letters in the various alphabets, linguists have created systems such as the International Phonetic Alphabet (IPA) to assign a unique symbol to each possible consonant sound.
Consonants can be categorized by the parts of the vocal tract that are used to make the proper sound. For example, labial consonants are those that use the lips to make the correct sound. Coronal and dorsal consonants use the front and middle parts of the tongue, respectively. Other types of consonants use parts such as the base of the tongue, the teeth and the vocal cords. There also are subcategories that are more specific, and some sounds use a combination of these parts.