"Peter works hard."

Translation: पीटर मेहनत करता है ।

[Maya925906]

Why is it not पीटर मेहनत काम करता है ?

[vinay92]

'मेहनत करना' itself means working hard.

You can say पीटर मेहनत का काम करता है but that has a different meaning - Peter does work that is hard.