Understanding English Diphthongs and Triphthongs

Understanding Diphthongs

A diphthong is a complex vowel sound consisting of two components. The first part is the main strong component (the nucleus), while the second part is short and weak (the glide). Together, the nucleus and the glide form one indivisible vowel sound within a single syllable.

Examples of Diphthongs

Diphthongs are always stressed on their first main component. Examples of one-syllable words include:

• [aɪ]: ride, right, lie, buy
• [aʊ]: brown, cloud
• [eɪ]: late, pray, pain, straight
• [ɔɪ]: toy, spoil

The RP Phonemic System

While linguistic sources vary, the Received Pronunciation (RP) system generally includes eight diphthongs: [aɪ] (ride), [aʊ] (now), [eɪ] (train), [ɔɪ] (boy, boil), [əʊ] (no, cold), [ɪə] (beer, here), [eə] (care, bear), and [ʊə] (tour, sure).

Classification of Diphthongs

Diphthongs are classified into two categories:

Closing Diphthongs

In closing diphthongs, the glide moves from an open vowel to a close vowel, shifting the tongue upwards. These include: /eɪ/ (day), /aɪ/ (die), /ɔɪ/ (boy), /əʊ/ (vow), and /aʊ/ (house).

Centring Diphthongs

In centring diphthongs, the glide moves from a front or back vowel toward the central schwa vowel /ə/, shifting the tongue toward the center of the mouth. These include: /ɪə/ (beer), /ɛə/ (where), and /ʊə/ (poor).

Vowel Glides and Minimal Pairs

A diphthong is a glide from one pure vowel to another. For instance, the word "the" contains the schwa sound /ə/, whereas "though" contains an amalgam of /ə/ and /ʊ/. Consequently, "the" and "though" can form a minimal pair in a weak position.

Understanding Triphthongs

Triphthongs are defined as a combination of three vowel sounds within a single syllable. English contains five triphthongs, each consisting of a closing diphthong followed by a schwa:

• /eɪə/ (player)
• /aɪə/ (fire)
• /ɔɪə/ (employer)
• /əʊə/ (slower)
• /aʊə/ (flower)

Smoothing and Reduction

As a general rule, the central element of a triphthong (/ɪ/ or /ʊ/) is reduced significantly. For example, in /eɪə/, the tongue moves only slightly toward /ɪ/ before continuing to /ə/. This phenomenon, known as smoothing, leads to the following simplifications: /eɪə/ to /eə/ (player), /aɪə/ to /aə/ (fire), /əʊə/ to /ə:/ (lower), and /aʊə/ to /aə/ (flower).