A diphthong is a vowel combination in a single syllable where the tongue moves from one vowel position to another in a smooth transition, creating a sound interpreted as a single phoneme. Diphthongs are represented by two vowel symbols indicating the starting and ending tongue positions. A monophthong is a pure vowel sound with a fixed articulation that does not change positions. There are 12 pure vowels in English classified by tongue height, frontness, and lip rounding. Common English diphthongs include /ei/ as in "late" starting at /e/ and moving to /i/, and /ai/ as in "rain" starting at the open vowel /a/.

2. 

In phonetics, a diphthong
literally "with two sounds," or
"with two tones") is a vowel
combination in a single syllable
involving a quick but smooth
movement from one vowel to
another, often interpreted by
listeners as a single vowel sound
or phoneme.
Diphthongs are represented by
two symbols, for example English
"same" as /seim/, where the two
vowel symbols are intended to
represent approximately the
beginning and ending tongue
positions.

3. 

The first letter shows
the starting point and
the second indicates the
direction of movement.
The terms, closing and
centering, refer to the
tongue position when it
produces those sounds.

4. • A monophthong is a "pure"
vowel sound, one whose articulation
at both beginning and end is
relatively fixed, and which does not
glide up or down towards a new
position of articulation; compare
diphthong.
•There are 12 pure vowels:
•Neutral Lips Vowels (/i:/,
/I/, /e/, /{ /, /A:/, /ö/,
/Æ:/, /@/)
•Lip-Rounding Vowels
(/O/, /O:/, /U/, /u:/)

5. /ei / is the so-called ‘long’ sound of the
letter a as in came /keim/.
The diphthong /ei / starts at about the
English /e/ or Vowel No. 3 and moves in
the direction of /i/ or Vowel No. 2.
Example: a – late /leit/, waste /weist/
ai, ay – rain /rein/, day /dei /
ei, ey – eight /eit/, they /Dei /
ea – great /greit/, break /breik/
exceptional: gauge /geiD/

6. •
•
Features:
• height of tongue: between halfopen and open
• part of the tongue which is
highest: the ‘front’
• position of lips: spread or
neutral
• opening between the jaws:
medium to wide
Examples:
› a – glad /gl{ d/, cat /k{ t/
› ai – plait /pl{ t/, plaid /pl{ d/

7. •
•
Features:
• height of tongue: between halfopen and open
• part of the tongue which is
highest: the ‘front’
• position of lips: spread or
neutral
• opening between the jaws:
medium to wide
Examples:
› a – glad /gl{ d/, cat /k{ t/
› ai – plait /pl{ t/, plaid /pl{ d/