Diphthongs: ei, ai, au, eu, äu

1.Two letters, one sound

A diphthong is two vowel letters that make one gliding sound in one syllable. The pair is read as a unit, not as two separate vowels stacked in a row.

mein is not e plus i. Haus is not a plus u. The two letters belong together.

German A1 has five common spellings and three sounds:

ie is not in this table. ie is long i, not a diphthong.

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2.One unit, one syllable

A diphthong stays inside one syllable. Splitting the two letters into two vowels breaks the word.

mein is one syllable. Reise is Rei-se: the diphthong is the first syllable, se the second. Auto is Au-to. heute is heu-te.

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3.ei and ai: the same sound

ei and ai are two spellings of one sound — the sound of mein and Mai. The ear cannot tell which spelling is written; the spelling belongs to the word.

ei is the normal spelling. Most A1 words use it:

ai is rare. At A1 it appears in a small set of words, often names or calendar words:

mein is ei. Mai is ai. Same sound, different stored spelling.

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4.ei is not ie

This is the main contrast for A1 reading. The same two letters appear in opposite order — and the readings are completely different.

sie is long i. sei is the diphthong. die is long i. drei is the diphthong. The group is read as a whole, not letter by letter.

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5.au

au is its own sound — the sound of Haus. At A1 there is no second spelling for this diphthong.

Related forms often change au to äu:

The new spelling is äu. The sound then becomes the eu/äu sound, not au.

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6.eu and äu: the same sound

eu and äu are two spellings of one sound — the sound of neu and Häuser. äu is not ä plus u, and it is not a long ä.

eu in the stem — words simply written with eu, usually without an au partner:

äu from au — forms that sit next to an au base:

When this sound is heard, the spelling is eu or äu. Which one depends on the word, and often on whether an au form sits beside it: Haus / Häuser, while neu has no nau.

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7.Diphthongs and ß

A diphthong counts as a long vocalic unit, so ß can stand after it. ss would mark a short vowel; a diphthong is not short.

That is why heißen has ß, not ss.

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8.How they sit in the word

The diphthong is the vowel of its syllable. Consonants around it behave as usual.

Typical shapes: klein is kl + ei + n; Freund is Fr + eu + nd; Deutsch is D + eu + tsch.

eu in Deutsch is still the diphthong. tsch is a consonant group after it, not part of the vowel.

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9.Five spellings, three readings

When two vowel letters stand together, the group is decided first:

1. ie → long i (not a diphthong)
2. ei or ai → the mein / Mai sound
3. au → the Haus sound
4. eu or äu → the neu / Häuser sound

Liebe — ie → long i.
bleiben — ei → diphthong.
Mai — ai → same diphthong as ei.
Haus — au.
Bäume — äu, same sound as eu.
heute — eu.

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10.Typical mistakes

Common weak readings and spellings:

• reading ei as ie — drei is not drie; heißen does not start like hier;
• reading the two letters separately — me-in, Ha-us, ne-u; the group is one sound;
• reading äu as long ä — Häuser does not start like Käse; it starts like neu;
• guessing ei vs ai from the sound — there is nothing to hear; Mai is a stored spelling;
• writing eu in a plural that belongs to au — Heuser; the plural of Haus is Häuser, with äu.