German comparatives — bigger, biggest, as big as

English has two ways to compare — bigger but more expensive — and you have to know which adjective takes which. German has one way. Every adjective, however long, takes the ending.

Mein Auto ist schneller. — My car is faster.

Das ist am schnellsten. — That is the fastest.

There is no mehr interessant. It is interessant → interessanter → am interessantesten, however long the word gets.

Short adjectives add an umlaut

Most one-syllable adjectives with a, o or u umlaut in the comparative and superlative.

Not all of them do — klar stays klarer, and so do most borrowed words. The ones that umlaut are common enough to learn by meeting them.

The six irregulars

These are worth memorising outright, because they are the ones you will use constantly.

gern → lieber → am liebsten is the one English has no equivalent for. It compares how much you like doing something:

Ich trinke gern Kaffee, aber lieber Tee. — I like coffee, but I prefer tea.

Am liebsten trinke ich Wasser. — Most of all I drink water.

als, not wie

The word for "than" is als.

Berlin ist größer als Hamburg. — Berlin is bigger than Hamburg.

wie is for "as ... as", with so in front:

Berlin ist so groß wie Paris. — Berlin is as big as Paris.

Das ist nicht so teuer wie ich dachte. — That is not as expensive as I thought.

Mixing these up — größer wie — is a mistake German speakers make too, which is why you will hear it. It is still counted as wrong in writing.

In front of a noun, it takes case endings as well

Everything above is the form used after sein. In front of a noun, the comparative behaves like any other adjective and adds the usual ending on top.

ein schnelleres Auto — a faster car

der schnellste Wagen — the fastest car

Note that the superlative in front of a noun drops am and takes der/die/das. The endings themselves come from the usual system — see German adjective endings.

immer plus comparative

To say something is increasingly so, German repeats immer:

Es wird immer kälter. — It is getting colder and colder.

Die Tage werden immer länger. — The days are getting longer and longer.

What to actually memorise

The six irregulars, and als for than. The -er / am -sten pattern needs no memorising at all — it is one rule with no exceptions about which adjectives it applies to, which makes this one of the few areas where German is straightforwardly easier than English.