Prepended Concatenation Mark

Prepended Concatenation Mark is a character property that identifies a small set of spacing symbols, such as the Arabic sign Sindhi ampersand or the Adlam punctuation marks, which are written before the number or word they modify but are visually separate from it. These marks function as prefixes in layout, yet they are not part of the base text’s logical order; instead, they are concatenated to the following character for rendering. This property affects line breaking, justification, and text segmentation, ensuring that the mark stays attached to the ensuing grapheme cluster without being treated as an independent word. It is particularly important for correct display in right-to-left scripts, where the mark appears at the start of a numeric sequence or phrase, and for search or collation, as the mark is ignored for sorting. Only a handful of characters possess this trait, making it highly specific and crucial for proper typographic behavior in certain writing systems.