German words ending in -er

-er usually means der, and usually is doing a lot of work in that sentence.

der Klaus the character this deck pins every der-word on

Two thirds is a strange number for a rule. It is high enough that guessing der on an -er noun beats guessing at random, and low enough that you will be wrong roughly once in three. No other page will tell you that, because most of them state -er as a rule and move on.

The reliable part of -er is the agent ending: take a verb, add -er, get the person or the thing that does it. Fahren gives der Fahrer, lehren gives der Lehrer, drucken gives der Drucker. That is genuinely masculine and you can trust it.

Everything else ending in -er is a coincidence of spelling. Das Wasser, das Fenster, das Zimmer, die Mutter, die Schwester, das Messer. These are not agent nouns, so the ending is telling you nothing, and the only thing that helps is knowing them individually.

The useful test is whether the word answers "the one that does the verb". If it does, der is safe. If it does not, you are guessing, and the list below is what you are guessing against.

Worked examples

der Lehrer teacher
der Drucker printer
der Computer computer
das Wasser water
die Mutter mother
das Fenster window

Measured on this deck

68% of the 154 nouns ending in -er are der

Across this deck, 104 nouns ending in -er are der and 50 are not. That is 68 percent, measured on a finite exam syllabus rather than on the dictionary. A gap that size earns a page, not a line in a rules table.

der Absender die Absender
der Anrufbeantworter die Anrufbeantworter
der Ausländer die Ausländer
der Bruder die Brüder
der Computer die Computer
der Drucker die Drucker
der Empfänger die Empfänger
der Fahrer die Fahrer
der Fehler die Fehler
der Großvater die Großväter
der Hunger
der Koffer die Koffer

and 92 more in the deck. Try the drill.

The ones that break it

50 of them, and the sample below is worth reading rather than skimming. Every one is a noun that ends in -er and is not der, and there is no shorter way to know them than to know them.

das Alter die Alter
das Bier die Biere
die Butter
das Doppelzimmer die Doppelzimmer
das Einzelzimmer die Einzelzimmer
das Feuer die Feuer
das Fieber die Fieber
die Geschwister die Geschwister
die Großmutter die Großmütter
das Meer die Meere
die Mutter die Mütter
die Nummer die Nummern

and 38 more in the deck. Try the drill.

What a card looks like

Lehrer

Try it

No rule wins this one for you. The drill below is the mixed deck, the condition that makes -er hard. Before the ending can tell you anything you have to decide whether the word in front of you is an agent noun at all.

Wohnung