How to guess; Der, Die or Das?
Introduction
Most world languages have nouns that are either masculine or feminine. German, besides capitalizing all nouns, goes them one better and adds a third gender: neuter. The masculine definite article (“the”) is der, feminine is die, and neuter is das. German-speakers just seem to know whether Wagen (car) is der or die or das. (It’s der Wagen.) And they also know that the other German word for car is das Auto. But when referring to cars by brand name, it’s always der Ford, der VW or der Mercedes.
It’s not the actual person, place or thing that has gender in German, but the WORD that stands for the actual thing. That’s why a “car” can be either das Auto (neut.) or der Wagen (masc.).
Forget linking gender to a specific meaning or concept. Although nouns for people often follow natural gender, there are exceptions such as das Mädchen, girl. There are three different German words for “ocean” or “sea”—all a different gender: der Ozean, das Meer, die See! And gender does not transfer well from one language to another. The word for “sun” is masculine in Spanish (el sol) but feminine in German (die Sonne). A German moon is masculine (der Mond), while a Spanish moon is feminine (la luna). It’s enough to drive an English-speaker crazy!
General rule
When learning a German noun, always treat its article as an integral part of the word! Not Wasser, but das Wasser. Not Hund, but der Hund. However, it can be very helpful to know about the gender generalizations below.
The German Plural
One easy aspect of German nouns is the article used for noun plurals. All German nouns, regardless of gender, become die in the nominative and accusative plural. So a noun such as das Jahr (year) becomes die Jahre (years) in the plural. Sometimes the only way to recognize the plural form of a German noun is by the article: das Fenster (window) – die Fenster (windows).
Der (MÄNNLICH)
Always MASCULINE (der/ein):
* Days, months, and seasons:
Montag, Juli, Sommer (Monday, July, summer). The one exception is das Frühjahr, another word for der Frühling, spring.
* Points of the compass, map locations and winds:
Nordwest(en) (northwest), Süd(en) (south), der Föhn (warm wind out of the Alps), der Scirocco (sirocco, a hot desert wind).
* Precipitation:
Regen, Schnee, Nebel (rain, snow, fog/mist)
* Names of cars and trains:
der VW, der ICE, der Mercedes. (But motorbikes and aircraft are feminine.)
* Words ending in -ismus:
Journalismus, Kommunismus, Synchronismus (equal -ism words in English)
* Words ending in -ner:
Rentner, Schaffner, Zentner, Zöllner (pensioner, [train] conductor, hundred-weight, customs collector). The feminine form adds -in (die Rentnerin).
* The basic “atmospheric” elements that end in -stoff:
der Sauerstoff (oxygen), der Stickstoff (nitrogen), der Wasserstoff (hydrogen), plus carbon (der Kohlenstoff). The only other elements (out of 112) that are masculine are der Phosphor and der Schwefel (sulphur).
Note: All of the other chemical elements are neuter (das Aluminium, Blei, Kupfer, Uran, Zink, usw.).
Usually MASCULINE (der/ein):
* Agents (people who do something), most occupations and nationalities:
der Architekt, der Arzt, der Deutsche, der Fahrer, der Verkäufer, der Student, der Täter (architect, physician, German [person], driver, salesman, student, perpetrator). Note that the feminine form of these terms almost always ends in -in (die Architektin, die Ärztin, die Fahrerin, die Verkäuferin, die Studentin, Täterin, but die Deutsche).
* Nouns ending in -er, when referring to people (but die Jungfer, die Mutter, die Schwester, die Tochter, das Fenster)
* Names of alcoholic drinks:
der Wein, der Wodka (but das Bier)
* Names of mountains and lakes:
der Berg, der See (but Germany’s highest peak, die Zugspitze follows the rule for the feminine ending -e, and die See is the sea).
* Most rivers outside of Europe:
der Amazonas, der Kongo, der Mississippi (See World Rivers in German)
* Most nouns ending in -ich, -ling, -ist:
Rettich, Sittich, Schädling, Frühling, Pazifist (radish, parakeet, pest/parasite, spring, pacifist)
Die (WEIBLICH)
Always FEMININE (die/eine):
* Nouns ending in the following suffixes:
-heit, -keit, -tät, -ung, -schaft – Examples: die Freiheit, Schnelligkeit, Universität, Zeitung, Freundschaft (freedom, quickness, university, newspaper, friendship). Note that these suffixes usually have a corresponding English suffix, such as -ness (-heit, -keit), -ty (-tät), -ship (-schaft).
* Nouns ending in -ie:
Drogerie, Geographie, Komödie, Industrie, Ironie (often equal to words ending in -y in English)
* Names of aircraft, ships and motorbikes:
die Boeing 747, die Titanic, die BMW (motorbike only; the car is der BMW). The die comes from die Maschine, which can mean plane, motorbike and engine. – Helpful reminder: Ships are often referred to as “she” in English.
* Nouns ending in -ik:
die Grammatik, Grafik, Klinik, Musik, Panik, Physik
* Borrowed (foreign) nouns ending in:
-ade, -age, -anz, -enz, -ette, -ine, -ion, -tur: Parade, Blamage (shame), Bilanz, Distanz, Frequenz, Serviette (napkin), Limonade, Nation, Konjunktur (economic trend). Note: Such words often resemble their English equivalent. A rare -ade exception: der Nomade.
* Cardinal numbers:
eine Eins, eine Drei (a one, a three)
Usually FEMININE (die/eine):
* Nouns ending in -in that pertain to female people, occupations, nationalities:
Amerikanerin, Studentin (female American, student), but der Harlekin and also many non-people words: das Benzin, der Urin (gasoline/petrol, urine).
* Most nouns ending in -e:
Ecke, Ente, Grenze, Pistole, Seuche (corner, duck, border, pistol, epidemic), but der Deutsche, das Ensemble, der Friede, der Junge ([the] German, ensemble, peace, boy)
* Nouns ending in -ei:
Partei, Schweinerei (party [political], dirty trick/mess), but das Ei, der Papagei (egg, parrot).
* Most types of flowers and trees:
Birke, Chrysantheme, Eiche, Rose (birch, chrysanthemum, oak, rose), but der Ahorn, (maple), das Gänseblümchen (daisy), and the word for tree is der Baum
* Borrowed (foreign) nouns ending in -isse, -itis, -ive:
Hornisse, Initiative (hornet, initiative)
Das (SÄCHLICH)
Always NEUTER (das/ein):
* Nouns ending in -chen or -lein:
Fräulein, Häuschen, Kaninchen, Mädchen (unmarried woman, cottage, rabbit, girl/maiden)
* Infinitives used as nouns (gerunds):
das Essen, das Schreiben (eating/food, writing)
* Almost all of the 112 known chemical elements (das Aluminium, Blei, Kupfer, Uran, Zink, Zinn, Zirkonium, usw.) – except for six that are masculine:
der Kohlenstoff (carbon), der Sauerstoff (oxygen), der Stickstoff (nitrogen), der Wasserstoff (hydrogen), der Phosphor and der Schwefel (sulphur). Note: Most of the elements end in -ium, a das ending.
* Names of hotels, cafés and theaters
* Names of colors used as nouns:
das Blau, das Rot (blue, red)
Usually NEUTER (das/ein):
* Geographic place names (towns, countries, continents):
das Berlin, Deutschland, Brasilien, Afrika (but learn non-das countries, such as: der Irak, der Jemen, die Schweiz, die Türkei, die USA [plur.])
* Young animals and people:
das Baby, das Küken (chick); but der Junge (boy).
* Most metals:
Aluminium, Blei, Kupfer, Messing, Zinn (aluminium, lead, copper, brass, tin/pewter; but die Bronze, der Stahl – bronze, steel)
* Nouns ending in -o (often cognates from Latin):
das Auto, Büro, Kasino, Konto (account), Radio, Veto, Video – Note: Exceptions: die Avocado, die Disko, der Euro, der Scirocco, etc.
* Fractions:
das/ein Viertel (¼), das/ein Drittel (but die Hälfte, half)
* Most nouns starting with Ge-:
Genick, Gerät, Geschirr, Geschlecht, Gesetz, Gespräch (back of the neck, device, dishes, sex/gender, law, conversation), but there are many exceptions, such as der Gebrauch, der Gedanke, die Gefahr, der Gefallen, der Genuss, der Geschmack, der Gewinn, die Gebühr, die Geburt, die Geduld, die Gemeinde, die Geschichte, and others)
* Most borrowed (foreign) nouns ending in -ment:
Ressentiment, Supplement (but der Zement, der/das Moment [2 diff. meanings])
* Most nouns ending in -nis:
Versäumnis (neglect; but die Erlaubnis, die Erkenntnis, die Finsternis)
* Most nouns ending in -tum or -um: Christentum, Königtum (Christianity, kingship; but der Irrtum, der Reichtum – error, wealth)
Source : about.com