The -ecek / -acak future participle
Turkish has three relative-clause participles. You've met the present subject participle -en (lesson 30) and the past/object participle -dık (lesson 31). The third is -ecek / -acak — the future participle. It works just like its siblings, but the relative clause has a future flavor: 'the X that will V' or 'the X to V'. Yapacağım iş = the work I'll do / the work for me to do. Gelecek hafta = next week (literally 'the coming/upcoming week'). Okuyacağın kitap = the book you'll read. Same logic as -dık, just shifted to the future.
How to form it
Drop -mek/-mak, add -ecek (after e/i/ö/ü) or -acak (after a/ı/o/u). Final -k softens to -ğ- before any vowel suffix, just like -dık: yapacak → yapacağ- before vowels. Then add the appropriate possessive ending matching the inner subject. yapmak → yap- + -acağ- + -ım → yapacağım = the (one) I'll do. gelmek → gel- + -eceğ- + -im → geleceğim = the (one) I'll come (to). okumak → oku-y-acağ-ım → okuyacağım (buffer -y- since stem ends in vowel).
Both subject AND object roles
Unlike -en (subject only) and -dık (everything-but-subject), -ecek can fill either role — it's the future-participle catch-all. Gelecek adam = the man who'll come (subject). Yapacağım iş = the work I'll do (object). When the inner subject is the head noun, no possessive is added — it works like -en. When the head noun is something else, add a possessive matching the inner subject — like -dık. Konuşacak kişi = the person who'll speak (subject). Konuşacağın kişi = the person you'll speak to (oblique with 2sg possessive).
The standalone use: 'next', 'upcoming'
-ecek/-acak without a possessive is the everyday word for 'next' or 'upcoming' in time expressions: gelecek hafta = next week, gelecek ay = next month, gelecek yıl = next year, gelecek pazartesi = next Monday. Gelecek alone also means 'the future' as a noun: Geleceğim parlak. = My future is bright. (Note the possessive: gelecek + -im = my future, again with the -k → -ğ- softening.)
Negative: -meyecek / -mayacak
Insert -me/-ma before the participle: -meyecek / -mayacak. Anlamayacağı şeyi söyleme. = Don't say something he won't understand. Yapmayacağım iş = work I won't do. Gelmeyecek misafir = a guest who won't come. The buffer -y- appears after -me/-ma because they end in vowels.
Hidden meanings: necessity and obligation
-ecek + possessive on its own (without a head noun) often signals 'something to V' — a thing that needs doing. Yapacağım çok iş var. = I have a lot of work to do. Söyleyeceğin bir şey var mı? = Is there something you want to say? Konuşacaklarımız çok. = There's a lot for us to talk about. This 'something to-V' nuance is one of the most useful patterns in everyday Turkish.
Quick contrast: all three participles together
Same verb yazmak, three participles: yazan = (the one) writing / who writes (-en, subject, present). yazdığım = (the one) I wrote / write (-dık, object, past/present). yazacağım = (the one) I'll write (-ecek, future). And the head noun: yazan adam = the man writing. yazdığım kitap = the book I wrote. yazacağım mektup = the letter I'll write. The possessive -ım on -dığım and -acağım marks 'I' as the inner subject.
