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Why 'alt' becomes 'älter': adjectives that add an umlaut

In English, you make a comparative by adding -er and leaving the rest of the word alone: old, older, oldest. German also adds -er and -(e)st, but many short, everyday adjectives change their vowel too. The a, o or u gets an umlaut: alt becomes älter, groß becomes größer and jung becomes jünger.

English never changes the vowel in a comparative, so learners often forget the umlaut. The result, for example alter or kalter, is a real German word, but it is not a comparative. It is just alt or kalt with an ordinary ending. So der alte Mann means the old man, while der ältere Mann means the older man. Getting the vowel right is what makes your comparison clear.

Word list
altA1 old älter armA1 poor ärmer großA1 big größer großA1 tall größer hochA1 tall höher (c drops) jungA1 young jünger kaltA1 cold kälter kurzA1 short kürzer kurzA1 short kürzer langA1 long länger langA1 long länger rotA1 red röter (also roter) schwarzA1 black schwärzer starkA1 strong stärker warmA1 warm wärmer gesundA2 healthy gesünder (also gesunder) krankA2 sick kränker nassA2 wet nässer (also nasser) schwachA2 weak schwächer altB1 ancient älter altB1 stale älter (altes Brot, das Brot von gestern ist noch älter) dummB1 stupid dümmer dummB1 silly dümmer glattB1 smooth glätter (also glatter) hartB1 strict härter klugB1 smart klüger klugB1 intelligent klüger scharfB1 sharp schärfer scharfB1 spicy schärfer schmalB1 narrow schmäler (also schmaler) blassB2 pale blässer (also blasser) scharfB2 sharp schärfer glattC1 slippery glätter (also glatter) scharfC1 sharp schärfer scharfC1 sharp schärfer scharfC1 sharp schärfer
How it works

The umlaut appears in both the comparative and the superlative, and it stays when you add adjective endings:

  • alt, älter, am ältesten (der ältere Bruder, die älteste Tochter)
  • groß, größer, am größten (only -t, not -est)
  • jung, jünger, am jüngsten

A useful rule of thumb: short, common adjectives of one syllable with a, o or u often take the umlaut. Longer adjectives almost never do. Words that already have an umlaut, such as schändlich, simply add endings.

Not every short adjective follows the pattern. Flach becomes flacher, fett becomes fetter and kahl becomes kahler. That is why it is best to learn the adjectives below as a list.

Mein Bruder ist zwei Jahre älter als ich.
(My brother is two years older than me.)
Meine jüngere Schwester wohnt noch zu Hause.
(My younger sister still lives at home.)
The words
Age and size

alt (in both the old and the ancient sense), jung, groß (big, and tall for people), lang and kurz (for both distance and time), and hoch. Note that hoch also loses its c: höher, am höchsten.

Paul ist schon größer als sein Vater.
(Paul is already taller than his father.)
Im Sommer sind die Tage länger.
(In summer the days are longer.)
Der Weg durch den Park ist kürzer.
(The path through the park is shorter.)
Das neue Hochhaus ist höher als die Kirche.
(The new tower block is higher than the church.)
Temperature

kalt and warm.

Im Winter ist es hier kälter als in Spanien.
(It's colder here in winter than in Spain.)
Morgen wird es endlich wärmer.
(Tomorrow it will finally get warmer.)
Strength and health

stark, schwach, krank and gesund.

Mit Training wirst du stärker, ohne Training schwächer.
(With training you get stronger, without it weaker.)
Gestern war ich noch kränker als heute.
(Yesterday I was even sicker than today.)
Obst ist gesünder als Chips.
(Fruit is healthier than crisps.)
Money and brains

arm, klug and dumm.

Er ist viel klüger, als er aussieht.
(He's much cleverer than he looks.)
Nach der Reise waren wir ärmer, aber glücklich.
(After the trip we were poorer, but happy.)
Sharpness

scharf becomes schärfer in all its meanings: a knife, a photo, eyes, pain, a pencil and spicy food.

Das Curry ist heute schärfer als letzte Woche.
(The curry is spicier today than last week.)
Watch out
Optional umlauts

Some adjectives allow both forms. Gesünder is more common than gesunder. With nass, blass, glatt and schmal, the forms without an umlaut (nasser, blasser, glatter, schmaler) are more usual today. The forms nässer, blässer, glätter and schmäler are also correct.

Completely irregular forms are a separate topic: gut, besser, viel, mehr and gern, lieber change the whole word, not just the vowel. Another special case is nah, näher, am nächsten.

The typical mistake is writing alter, kalter or junger when you mean older, colder or younger. If you find yourself adding als, check the vowel.

Summary

When you compare with a short, everyday adjective that has a, o or u, expect an umlaut in both the comparative and the superlative: alt, älter, am ältesten, groß, größer, am größten, jung, jünger, am jüngsten. The umlaut stays when you add endings (der ältere Bruder). Learn the core list (alt, jung, groß, lang, kurz, hoch, kalt, warm, stark, schwach, krank, gesund, arm, klug, dumm, scharf) and remember that a few words, such as nass and schmal, allow both forms.