Every Arabic noun is either masculine (مذكر) or feminine (مؤنث). Adjectives must match the gender of the noun.
Default form — no special ending.
Examples: كِتَاب (kitab - book) · رَجُل (rajul - man) · بَيْت (bayt - house)
Usually ends in ة (Ta Marbuta).
Examples: مَدْرَسَة (madrasa - school) · مَرْأَة (mar'a - woman) · غُرْفَة (ghurfa - room)
Some words are grammatically feminine by convention:
الكتاب الكبير (al-kitab al-kabir) — The big book (m)
المدرسة الكبيرة (al-madrasa al-kabeera) — The big school (f)