Hi "My car has broken down." Does it mean my car has something wrong with its engine? Could I use “break down” with my bike? "My bike has broken down." If it is possible, how could I understand “break down” with my bike? Thanks a lot.
Yes, pretty much any vehicle can "break down", Mimi. What it means is that it won't run. You don't necessarily even know what's wrong with it (until you get it fixed) but if it won't run, it's broken down.
A malfunction in your bicycle chain or brakes could cause your bicycle to "break down".
"Broken down" is usually reserved for mechanical things, Mimi (things with gears and sprockets and other archane parts). You would say "My watch has stopped" (it's not working). You would say "My fountain pen won't work" (it's not necessarily "broken" - it could just be out of ink). If I heard "My computer has broken down", I would think that phrase acceptable because there are so many components of a computer that could "break". Some computer geeks might argue with me on this but...
"Broken down" for a machine is similar to "in a coma" for a living being. The condition is not an easy one to get out of, and the expression applies mainly to machines larger than a breadbox. I think a computer qualifies if it's in serious trouble.
When you break a stick, for example, it may remain in one piece but broken, not intact, so when a machine is broken, it has, metaphorically speaking, lost integrity like the broken stick. When something breaks down, its integrity has "fallen" due to natural forces and it may take some effort to restore it.
Another metaphor/analogy: If a limb breaks, it may still be hanging together up in the tree, perhaps reparable with duct tape or whatever, but if it breaks down, it has fallen off, and repair is going to take more effort if it is possible at all.
"Down" for a machine means that it is completely out of service (maybe awaiting repair).