Diphthongs in English

The diphthong is a combination of two vowel sounds that are pronounced together and form one syllable.

[ai]

[ai] is expressed by vowels "i" and "y" in an open stressed syllable, by letter combinations "ie" and "ye" in the end of the word, as well as by "uy", "eye", "igh"

i - line [laɪn] 
y - fly [flaɪ] 
ie - tie [taɪ] 
ye - dye [daɪ] 
uy - guy [gaɪ]
igh - knight [naɪt] 

[ɔɪ]

In writing it is expressed by "oi" and "oy".

oi - noisy ['nɔɪzɪ]
oy - annoy [ə'nɔɪ] 

[eɪ]

It formed at the front part of the tongue. In writing it is expressed by letter "a" in the open stressed syllable, and by letter combinations "ai", "ay", "ey", "ea", "ei".

a - save [seɪv] 
ai - main [meɪn] 
ay - tray [treɪ] 
ey - grey [greɪ] 
ea - great [greɪt]
ei - eight [eɪt] 

[au]

This diphthong is pronounced together but sound "а" is longer that "у".
It is expressed in writing by letter combinations "ow", "ou".

ow - town [taun] 
ou - pound [paund] 

[əu]

It is written with letter "o" in an open stressed syllable, and letter combinations "ow", "ou", "oa", "o+ld", "o+ll"

o - bone [bəun] 
ow - snow [snəu] 
ou - soul [səul] 
oa - coat [kəut] 
old - cold [kəuld] 
oll - roller ['rəulə] 

[ɪə]

Sound [i] is pronounced longer than short sound [ə].
Letter combinations "ear", "eer", "ere", "ier" are used in writing.

ear - gear [gɪə] 
eer - deer [dɪə
ere - severe [sɪ'vɪə] 
ier - fierce [fɪəs] 

[ɛə]

Sound [i] is pronounced longer than short sound [ə].
Letter combinations "ear", "eer", "ere", "ier" are used in writing.

are - care [kɛə] 
ear - bear [bɛə] 
air - repair [rɪ'pɛə] 

[uə]

In writing it is transferred by letter combinations "are", "ear", "air".

ue - cruel [kruəl] 
ure - sure [ʃuə] 
our - tour [tuə]