Learn Turkish: Yolcu, tren sahil boyunca durmamış diye şikâyet etti. - The passenger complained because the train apparently did not stop along the coast.

The postposition boyunca means "along" when used with physical places like sahil (coast) or yol (road). When used with time words, like gün boyunca, it means "throughout" or "for the duration of" (all day). Here, sahil boyunca literally means "along the length of the coast". Also, notice that sahil stays in its bare form without any suffixes, which is the rule for this postposition.

Why is the verb durmamış in the -mış past tense instead of the regular -dı past tense?

The -mış tense is used here because the speaker is reporting someone else's claim. By saying durmamış, the speaker is conveying what the passenger alleged ("the train apparently didn't stop"), distancing themselves from the fact. If the speaker was stating it as an absolute fact they witnessed, they would use durmadı.

What role does diye play in this sentence?

diye comes from the verb demek (to say) and literally means "saying". It is frequently used to connect a quoted thought, statement, or reason to a main verb. Here, it links the passenger's claim (tren sahil boyunca durmamış) to the verb şikâyet etti (complained). In English, we naturally translate this structure as complaining because or that something happened.

Why is there a comma after ?