Khmer Sign Triisap

It shifts a consonant into the second vowel register. Khmer consonants belong to two series, called registers, that affect nearby vowel sounds. Triisap, also spelled treisap, shifts a first-register consonant to the second when the spelling calls for that series. Compare សក, meaning “peel,” with ស៊ក, “insert”: the mark helps spell a different word.

The Khmer script descends from Brahmi, an ancient South Asian writing system; early Khmer inscriptions, known from the 7th century, resemble the Pallava script of southern India. Khmer writing also influenced the development of Thai and Lao scripts. A historical study places the formation of Khmer’s two vowel registers around the 16th century, after older consonant contrasts changed.

Why can triisap look like vowel U?

Crowded syllables can give the shifter a vowel-U shape. Beside another mark above the consonant, triisap may be drawn below it using the same shape as the separate vowel sign ◌ុ. It is still triisap, not that vowel.

Enter it immediately after the base consonant, even when it displays below. In an expert sequence that must keep the raised form, place U+200C ZERO WIDTH NON-JOINER before triisap; ordinary Khmer text entry follows the standard order without that control.