Tetragraphs in Arrernte transcribe single consonants, but are largely predictable from their components.
⟨illi⟩ is pronounced [j] in words such as joaillier and quincaillier (which can also be written as joailler and quincailler since 1990).
⟨tsch⟩ represents [t͡ʃ], which is a relatively common phoneme in German, appearing in words like deutsch ("German"), Deutschland ("Germany"), Tschechien ("Czech Republic"), and tschüss ("bye").
There are several sequences of four letters in the Romanized Popular Alphabet that transcribe what may be single consonants, depending on the analysis.
⟨dcgʼ⟩ for [ᶢǀʢ] ⟨dçgʼ⟩ for [ᶢǂʢ] ⟨dqgʼ⟩ for [ᶢǃʢ] ⟨dxgʼ⟩ for [ᶢǁʢ] Piedmontese does not have tetragraphs.
⟨gqxʼ⟩ is used in the practical orthography of the Taa language, where it represents the prevoiced affricate [ɢqχʼ].
However, the apostrophe is a diacritic in Swahili, not a letter, so this is not a true tetragraph.
⟨s-ch⟩ is used in the Puter orthographic variety of the Romansh language (spoken in the Upper Engadin area in Switzerland) for the sequence /ʃtɕ/ (while the similar trigraph ⟨sch⟩ denotes the sounds /ʃ/ and /ʒ/).