The vowels on Figure 3 are so-called primary cardinal vowels and these are the vowels that are most familiar to the
speakers of most European languages. For example, cardinal vowel no. 1 has the symbol [i], and is defined as the vowel
which is as close and as front as it is possible to make a vowel without obstructing the flow of air enough to produce
friction noise. However, cardinal vowel no. 5 has the symbol [α] and is defined as the most open and back vowel that it
is possible to make.