Practically, the twofold pattern (also referred to as the e-type vowel harmony) means that in the environment where the vowel in the word stem is formed in the front of the mouth, the suffix will take the e-form, while if it is formed in the back it will take the a-form. The fourfold pattern (also called the i-type) accounts for rounding as well as for front/back. The following examples, based on the copula "-dir"4 (" is"), illustrate the principles of i-type vowel harmony in practice: "Türkiye'dir" ("it is Turkey"), "kapıdır" ("it is the door"), but "gündür" ("it is the day"), "paltodur" ("it is the coat").