Have you ever said words like "boy," "toy," or "coin" out loud and noticed something unique about the vowel sound? If so, you've encountered a diphthong – a vowel that contains two different sounds in one syllable.
In contrast, a monophthong is a single, pure vowel sound. The word "diphthong" comes from the Greek words di, meaning "two," and phthong, meaning "sound," making it quite literally a "two-sound" vowel.
Diphthongs are known as gliding vowels, as one sound glides into the next. Typically, the first vowel is longer and stronger than the second in the English language.
One example of a diphthong is /ɔɪ/, pronounced as the "oi" sound in words like "boy," "toy," or "coin." Try slowly saying these words and notice how your lips form a rounded and spread wide shape, without touching. This showcases how the two vowel sounds glide into each other.
However, not all words with two vowels in a row create a diphthong sound. For example, the word "feet" /fiːt/ does not have a diphthong but contains the monophthong /iː/, as seen in the longer "e" sound.
There are eight diphthongs in the English language, each represented by two separate symbols to indicate the two distinct vowel sounds. These symbols, found in the International Phonetic Alphabet or the English phonemic alphabet, are used to transcribe diphthongs. The eight diphthongs are:
Struggling to discern the two separate vowel sounds in these words? Don't worry – Diphthongs may seem unfamiliar because native English speakers tend to shorten them into single vowel sounds. Try pronouncing the words in a British accent – can you now hear the glide?
Linguists have classified the eight diphthongs into various types based on their sound production and pronunciation, including falling and rising diphthongs, opening and closing diphthongs, centring diphthongs, and wide and narrow diphthongs.
Falling diphthongs begin with a higher pitch and end with a lower one. A common example is /aɪ/ in words like "eye," "flight," and "kite."
Rising diphthongs start with a lower pitch and end with a higher one, produced when a vowel follows a semivowel, such as /j/ and /w/. There are no specific phonemic representations, as they are typically analyzed as a sequence of two phonemes. Examples include "yell" (/jel/), "weed" (/wiːd/), and "walk" (/wɔːk/).
Opening diphthongs have a second vowel sound that is more "open" than the first. For instance, /ia/ in the Spanish word "hacia" would sound like "yah" in English. On the other hand, closing diphthongs have a second vowel sound that is more "closed" than the first, such as /iː/ in "see."
It's worth noting that wide diphthongs, like /aɪ/ in "time" and /aʊ/ in "cow," require a larger tongue movement between vowel sounds, creating a more noticeable difference between the two sounds. In contrast, narrow diphthongs, such as /eɪ/ in "day," have a smaller movement between vowels, resulting in similar-sounding vowel sounds.
It's also important to distinguish between diphthongs and monophthongs.
A monophthong is a single vowel sound within a syllable, such as the /ɪ/ in "sit," /u:/ in "cool," and /ɔ:/ in "all." On the other hand, a diphthong is a combination of two vowel sounds in one syllable, also known as a gliding vowel, where the first sound glides into the second.
It is important to note that the presence of two vowels next to each other in a word does not always indicate a diphthong. For example, in "meat" (/miːt/), the two vowels form the monophthong /iː/, while in "time" (/taɪm/), the word is pronounced with the diphthong /aɪ/.
