This is the 979th most frequent Persian word.
سیاه
The Persian word "سیاه" means "black" in English.
Here, 'سیاه' (siyāh) is used as an adjective describing the color of the subject, the cat.
آن گربه سیاه در باغ راه میرود.
That black cat is walking in the garden.
In this context, 'سیاه' (siyāh) is used as an adjective to describe the change in appearance of the sky.
بعد از طوفان، آسمان سیاه شد.
After the storm, the sky turned black.
Here, 'سیاه' (siyāh) indicates the cultural significance of the color black in specific events.