This is the 11515th most frequent Spanish word.
extrañas
"Extrañas" means "you miss" (second person singular, present tense of "extrañar") or "strange/foreign" (feminine plural adjective).
Here, 'extrañas' is used as the second person singular form of the verb 'extrañar,' implying 'to miss someone or something.'
Extrañas mucho a tus amigos cuando estás lejos.
You miss your friends a lot when you are far away.
In this sentence, 'extrañas' functions as an adjective meaning 'strange' and modifies the noun 'luces.'
Vi luces extrañas en el cielo anoche.
I saw strange lights in the sky last night.
Once again, 'extrañas' is an adjective describing the noun 'cosas,' signifying 'strange.'