英语解释：One of the screws is loose.
有一颗螺丝松了。
a thin pointed piece of metal like a nail with a raised spiral line (called a thread ) along it and a line or cross cut into its head. Screws are turned and pressed into wood, metal, etc. with a screwdriver in order to fasten two things together. 螺丝钉；螺丝:
