This is the 570th most frequent Ukrainian word.
син
"Son."
The word "син" here means "son," referring to a male child of parents.
Мій син народився влітку.
My son was born in the summer.
The word "синім" (a form of "синій") here means "blue," describing the color of the sky.
Небо стало яскраво-синім перед заходом сонця.
The sky turned bright blue before sunset.
The word "син" here is part of an idiomatic expression or poetic device describing the blue hue of the ocean, suggesting a metaphorical or artistic usage.