牢牢 (láo láo): vững chắc

Mom firmly stuck her child's photo on the refrigerator door, so she could see it every time she cooked, and felt especially warm inside.

The climber tied his body firmly to the rock with a rope to prevent accidentally slipping and falling.

Although I graduated many years ago, the happy times I spent with friends in high school are still firmly etched in my memory.

The traffic police officer reached out and firmly grabbed the little boy who wanted to run the red light, patiently telling him that crossing the street that way was very dangerous.

You must firmly remember every clause in the contract, otherwise you might suffer a loss in the cooperation.