High Quality Content by WIKIPEDIA articles! Th is a digraph in the Roman alphabet. The most obvious use of the letter combination is to represent the juxtaposition of the phonemes /t/ and /h/, as in English hothouse. However, this is not strictly a digraph, as it is representing a consonant cluster rather than a single phoneme. As a digraph in the strict sense, was originally introduced in Latin, which had many Greek loan words, to transcribe the Greek letter Theta ( , ), which at that time originally represented the aspirated stop /t?/. Still today, is used in academic transcription systems to represent letters in oriental alphabets which have the value /t?/. According to Royal Thai General System of Transcription, for example, represents a series of Thai letters with the value /t?/.