الأنف مذكر، نقول: أنفه كبير وعادةً ما تكون أعضاء الجسم المزدوجة، مثل "أذن" و"عين" مؤنَّثة، والمفردة، مثل "أنف"، و"فم"، مذكَّرة

one thing about Arabic words is (as in French) they can be feminine or masculine: e.g: nose is masculine : أنف كبير and not أنف كبيرة eye is feminine: عين كبيرة and not عين كبير there is no such thing as a rule to know what words are feminine and what words are masculine, but there are some not basic rules: & - most words that has (ة) at the end are feminine (as in in french, where most words that end with (e) are feminine) e.g: وردة جميلة, امرأة قصيرة, رياضة متعبة (beautiful rose, short woman, tiring sport) in the first two examples it's pretty obvious that the words are feminine, but in the last example, the only clue for knowing it's a feminine word is the (ة) at the end. & - irregular plurals for "not human" words. that's a tricky rule, some words like (bird عصفور) when you want to make it in plural it becomes (birds عصافير ) which is an irregular plural, and it's treated as feminine (beautiful birds عصافير جميلة) & -and as Badr said in the first answer: when it comes to body parts, body parts that comes in pairs ( ears, eyes, legs) are treated as feminine, while parts that come as singles (nose, face, neck) are treated as masculine: e.g: paired parts: (big eye: عين كبيرة )(big hand: يد كبيرة ) singular parts: (big nose: أنف كبير)(wide face: وجه عريض) there are many special cases for that rule like: (flat stomach: معدة مسطحة ) but you might have figured that it is feminine from the (ة) at the end

some things are feminine and others not but in plural it's always feminine جبل كبير جبال كبير