"The lamp is expensive."

[Glossmad]

το φωτιστικό είναι ακριβό?

[Dimitra956826]

It's been added, thank you ^.^

[Kataphract]

I wrote "Το λάμπα είναι ακριβός" and it didn't accept, pointing out that i should've used "φωτιστικό" instead?

[Dimitra956826]

Don't forget about the genders ;)

The word λάμπα is feminine in gender, so the correct translation would be "η λάμπα είναι ακριβή".

(Φωτιστικό popped up because you used the article το. If there is a translation with the article you chose, then Duolingo doesn't mark the article as incorrect, but the noun -in this case, λάμπα)