Heng is a letter of the Latin alphabet, derived from h combined with something similar to eng.
It was used word-finally in early transcriptions of Mayan languages, where it may have represented a uvular fricative.
It is sometimes used to write Judeo-Tat.
It has been occasionally used by phonologists to represent a hypothetical phoneme in English, which includes both [h] and [ŋ] as its allophones, -- to illustrate the limited usefulness of minimal pairs to distinguish phonemes. Normally /h/ and /ŋ/ are considered separate phonemes in English, even though a minimal pair for them cannot be constructed, due to their complementary distribution.
Both U+A726 Ꜧ LATIN CAPITAL LETTER HENG (HTML Ꜧ) and U+A727 ꜧ LATIN SMALL LETTER HENG (HTML ꜧ) are encoded in Unicode block Latin Extended-D.
IPA usage
A variant form, U+0267 ɧ LATIN SMALL LETTER HENG WITH HOOK (HTML ɧ), is encoded as part of the IPA Extensions block. It is used to represent the voiceless palatal-velar fricative in the International Phonetic Alphabet.