"Rhaid i fi lanhau'r siop."

Translation: I must clean the shop.

[AbunPang]

Would it make a difference if I would say "Rhaid i fi olchi'r siop"?

[EllisVaughan]

Hmm, I would say so. "Glanhau" is more "To clean up" as in move things around to create a tidier space, whereas "Golchi" stimulates the idea of a bucket of soapy water, so you "golchi" the dishes and the car and the windows, but "glanhau" a room or a space.

[AbunPang]

Diolch am yr eglurhad!