tengre, n. letter (character), or any other character used in a writing system beyond alphabets.

usage: The concept of tengre includes letters (alphabetic characters), any other character used in writing systems beyond alphabets (syllabaries, semi-syllabaries, hieroglyphs, abugidas, etc.), as well as typical characters used in writing systems, such as accents, diaeresis, hyphens, circumflexes, and the like.