Electrical – Installing Pendant light which came with 3 clear wires and 1 copper/bare wire

This fixture is not wired per code, you should have only one white wire for each colored wire, you should never have only one colored wire and more than one white wire.

What the previous posters are suspecting is you have a three-way circuit so that two or more switches can control the fixture.

You can use a multi-tester of test light to see if you have current between the black wire and one of the white wires when the switch is turned on. If you have current through more than one white wire then stop and call an electrician. You might inadvertently overload a neutral. If your switch does not read on and off then you probably have a three-way circuit and you may need an electrician to sort it out.

If the old fixture worked, at least one of the white wires is hot.

The easiest way to check which is hot is to use a non-contact tester. If the fixture is already removed, leave the two wires bundled together with a wire nut over the end. Put a wire nut on the single white wire. Turn the breaker back on. Only one of those should register on tester. That is the hot side. The other should not register. That is the neutral.

Once you know which wire is hot, mark it with black tape or a permanent marker.

If the the fixture is still attached, you can do the same thing with the fixture hanging down. Once you know what is what, turn the breaker back off before wiring.

The black wire goes to the hot wire, the white to the neutral. The ground wire should be attached to a green or bare wire if there is one in the box, or to the box itself if it is metal. If not, just cap it.