"The seasons are spring, summer, autumn and winter."
Translation:Mevsimler, ilkbahar, yaz, sonbahar ve kıştır.
Yes, after a "ş", you use -tir. The suffixes that start with "d" or "c" change into "t" or "ç" after certain letters. There are a few mnemonics to memorize which letters trigger this change:
Fıstıkçı Şahap (Şahap the pistacchio seller)
Efe Paşa çok hasta (Efe Pasha is very ill)
Ketçap fahişesi (The ketchup prostitute)
When a word ends in one of the consonants in these phrases, any suffix that begins with a "d" or "c" will begin with a "t" or "ç" instead.
Regarding your last question; it would be incorrect indeed.
If you said: "Mevsimler ilkbahardır, yazdır, sonbahardır, kıştır.
That would be like saying: "The seasons are spring, are summer, are autumn, are winter.
For "ilkbahar" and "sonbahar", one way to distinguish and remember these similar looking words is to remember that another meaning for "bahar" is "blossom" so you can think of "ilkbahar" as literally "first-blossom (i.e. spring) and "sonbahar" as literally "last-blossom" (i.e. autumn)
aregdanago, please, read the clear comment of lisa4duolingo. She gives us very usefull links about the topic of "dir", "tir", etc...You'll always find the answer to your question, reading the comments of other advanced learners or contributors. I do it since the beginning; it's very usefull. We all have the same questions!
"Bahar" comes from the Persian word for "Spring." Its interesting to me because we don't have separate words for the first and last part of spring in Persian. It can be a female name as well.
Its the most cherished season not only in Iran, but in Turkey as well because of Nevruz/Nowruz.
I think, if I'm not mistaken, people generally use "bahar" in Turkey when conversing as oppose to "ilkbahar" (unless you want to be really specific about it).
The best way I can think of to explain it is to say that it is a suffix used in Turkish to express "to be" for the following points of view:
he/she/it is -dir/-tir -dır/-tır -dür/tür -dur/-tur (third person singular)
they are -dirler/-tirler -dırlar/-tırlar -dürler-/türler -durlar/-turlar (third person plural)
You can read more about this aspect of the Turkish language at the link below:
After visiting that page, you also may find the discussion at the following link useful:
Hope that helps.
Okay, so my answer "Mevsimlar ilkbahar, yaz, sonbahar, kisdir" was marked wrong because I didn't put the "ve" before "kisdir". I understand why it was marked as incorrect in this context, but I've also noticed that in (written) Turkish "ve" is apparently not used before the last item when there is a list of three or more things. Is that correct?