This is the 10154th most frequent Turkish word.
başlamamışlar
"They have not started."
Here, 'başlamamışlar' indicates that the act of starting talking has not been performed yet by a group of people in the past, reflecting the negative past perfect tense in Turkish.
Konuşmaya henüz başlamamışlar.
They haven't started talking yet.
In this context, 'başlamamışlar' refers to the action of starting the project, which has not yet occurred, linked causatively to the lack of a plan.
Projeye başlamamışlar çünkü bir planları yokmuş.
They haven't started the project because they didn't have a plan.
Here, 'başlamamışlar' is used to convey the speaker's assumption about the non-initiation of an event by a group of individuals.