Inproper polarity on horn wires. or horn relay bad. Ensure voltage (12VDC) on horn wire when activating horn. If nothing... suspect relay.
More than likely a stuck horn relay.
If the horn does not work in the 1998 Chevy Prism and the vehicle was purchased used in this condition, it is quite possible that the previous owner cut the horn wires to stop the annoying security alarm. It is also possible that the fuse for the horn is blown.
cut the cheese
The horn is on the left side under the corner of the bumper. If you take the bumper off you will know it when you see it.
Short in the wiring with the steering column.
Fuse panel. Read your owner's manual.
check the horn fuse
Because the other one is damaged. Usually water damage.
It's located at the front of the passenger front fender, inside the plastic splash shield. You would need to remove the horn to get to it.
Probably a short in the horn wire.
It is behind the headlight on some cars.
Tucked into the quarter panels on the front of the car