This is the 17623rd most frequent Russian word.
тяжёлой
The word "тяжёлой" in English means "heavy" (feminine form, instrumental or genitive case) or "difficult."
In this sentence, 'тяжёлой' is used as an adjective describing the textbook's physical weight.
У меня была тяжёлой учебник, и я устал носить его.
I had a heavy textbook, and I got tired of carrying it.
Here, 'тяжёлой' is used metaphorically to indicate the difficulty of the work.
После тяжёлой работы я люблю отдыхать на природе.
After hard work, I enjoy relaxing in nature.
In this case, 'тяжёлой' describes an emotional state, conveying a sense of burden or sorrow.