If you learn one thing properly in this course, make it this. Vowel harmony is the reason a Turkish ending appears in two, four or even eight shapes, and once you see the pattern you stop memorizing forms and start predicting them. Turkish vowels split into two teams. Front: e, i, ö, ü. Back: a, ı, o, u. An ending copies the team of the last vowel in the word — that is the whole idea. Two-way endings pick between e and a. Four-way endings pick between i, ı, u and ü, and there the ending also copies whether your lips were rounded. English does something related when it turns «in-» into «im-» before p and b (impossible, not inpossible): the ending adapts to the word. Turkish just does it everywhere, and does it out loud.
ev — evdeev has e, a front vowel, so «at home» is evDE. Front pulls front.
okul — okuldaokul ends in u, a back vowel, so «at school» is okulDA. Same ending, other team.
göz — gözdeö is front, so -de. The rule cares about the LAST vowel of the word, nothing else.
kitap — kitaptaa is back → -ta. And the d hardened to t after p. Two rules firing in one short word.
ev — evlerThe plural is also two-way: -ler after front vowels.
kitap — kitaplar-lar after back vowels. English has one plural -s; Turkish has one plural in two coats.
ev — evim«My house». The four-way ending picks i because e is front and unrounded.
okul — okulum«My school» — u because okul's last vowel is back AND rounded.
göz — gözüm«My eye» — ü because ö is front AND rounded. Your lips do the same thing twice in a row.
kız — kızım«My daughter» — ı because kız is back and unrounded. Four vowels, four situations, no exceptions.
kalem — kalemler — kalemlerimEndings stack in a fixed order and each one harmonizes with the one before it: pen → pens → my pens.
telefon — telefonlar — telefonlarımA loanword follows the same rule as a native one. Harmony has no favorites.
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