Monophthongs are also called ‘pure vowel sounds’ and they are 12 in number. They include:

1 i: see, unique, feel

2 ɪ wit, mystic, little

3 e set, meant, bet

4 æ pat, cash, bad

5 ɑ: half, part, father

6 ɒ not, what, cost

7 ɔ: port, caught, all

8 ʊ wood, could, put

9 u: you, music, rude

10 ʌ bus, come, but

11 ɜ: girl, word, fur

12 ə alone, butter

See: http://www.languagebits.com/phonetics-english/vowels-in-the-english-language/