This is the 2464th most frequent Arabic word.
مجهولة
"مجهولة" means "unknown" or "unspecified."
Here, 'مجهولة' (majhoola) is used as an adjective meaning 'unknown' describing places.
استمتعنا باستكشاف أماكن مجهولة داخل الغابة.
We enjoyed exploring unknown places in the forest.
In this sentence, 'مجهول' (majhool) is used as an adjective meaning 'unknown', describing the source of the letter.
تلقى خطابًا من مصدر مجهول.
He received a letter from an unknown source.
Here, 'المجهولة' (al-majhoola) is used as an adjective in the plural form with a definite article to mean 'the unknown things'.