This is the 938th most frequent Ukrainian word.
мозку
The Ukrainian word "мозку" means "brain" (genitive singular form).
In this sentence, 'мозку' is used in the dative case to indicate the brain as the indirect object of giving rest.
Мені потрібен час, щоб дати трохи відпочинку моєму мозку.
I need some time to give some rest to my brain.
Here, 'мозку' is in the dative case, showing the beneficiary of the exercise, which is the brain.
Розв'язування головоломок є добрим вправлянням для мозку.
Solving puzzles is a good exercise for the brain.
In this instance, 'мозку' is used in the genitive case to define the type of health being referred to, which belongs to the brain.