Arabic has two grammatical genders: masculine (مذكر) and feminine (مؤنث). Every noun in Arabic is either masculine or feminine, and this gender affects how verbs, adjectives, pronouns, and demonstratives interact with it. Understanding gender is fundamental to constructing grammatically correct Arabic sentences.
Many feminine nouns are marked by taa marboota (ة) at the end, such as مدرسة (school), طالبة (female student), and مدينة (city). However, not all feminine nouns have this marker. Some are feminine by meaning (أم = mother, أخت = sister), and some are inherently feminine by convention (شمس = sun, أرض = earth, نار = fire). These must be memorized individually.
Gender agreement is a critical rule in Arabic grammar. Adjectives must agree with the nouns they describe in gender. A masculine noun takes a masculine adjective (رجلٌ كبيرٌ = a big man), while a feminine noun takes a feminine adjective (امرأةٌ كبيرةٌ = a big woman). Similarly, verbs must agree with their subjects in gender.
There are some interesting exceptions and nuances. Broken plurals of non-human nouns are treated as feminine singular for grammatical agreement, regardless of the gender of the singular form. So you would say الكتبُ الجديدةُ (the new books), using the feminine singular adjective, even though كتاب (book) is masculine. This rule surprises many learners but becomes natural with practice.