[1] In German, for example, the tetragraph tsch represents the sound of the English digraph ch.
For example, the Cyrillic alphabets adapted to the Caucasian languages, which are phonologically very different from Russian, make extensive use of digraphs, trigraphs, and even a tetragraph in Kabardian кхъу for /q͡χʷ/.
The Romanized Popular Alphabet created for the Hmong languages includes three tetragraphs: nplh, ntsh, and ntxh, which represent complex consonants.
In Cyrillic used for languages of the Caucasus, there are tetragraphs as doubled digraphs used for 'strong' consonants (typically transcribed in the IPA as geminate), and also labialized homologues of trigraphs.
⟨кхъу⟩ is used in Kabardian for [qʷ], the labialized homologue of ⟨кхъ⟩ [q], in turn unpredictably derived from ejective ⟨къ⟩ [qʼ].