A character cluster is a collection of alphabetic characters forming a single word or syllable.
A Hebrew character cluster can contain characters and diacritics, though diacritics are not often used.
Character clusters are integral to written text in Thai. A Thai character cluster consists of up to four parallel lines:
Base line of consonant, vowel, or symbol
Lower line of lower vowel or diacritic
Upper line of upper vowel or diacritic
Line above the upper line for tone marks and upper diacritics
One or more elements may change shape in the presence of other elements. In the Thai language engine, a character cluster occupies one display cell. Depending on the composition, one display cell can contain up to three input characters, as shown in Figure 1-5.