Dieses Zeichen ist ein Nonspacing Mark und erbt seine Schrift-Eigenschaft vom vorhergehenden Zeichen. Es wird auch in der Schrift Griechisch verwendet.
Das Zeichen ist keine Zusammensetzung. Seine Weite in ostasiatischen Texten wird vom Kontext bestimmt. Es kann weit oder schmal sein. In bidirektionalem Text handelt es als Nonspacing Mark. Bei einem Richtungswechsel wird es nicht gespiegelt. U+0342 verbietet einen Zeilenumbruch vor sich. Der Buchstabe kann mit einem anderen Zeichen verwechselt werden.
Die Wikipedia hat die folgende Information zu diesem Codepunkt:
Greek orthography has used a variety of diacritics starting in the Hellenistic period. The more complex polytonic orthography (Greek: πολυτονικό σύστημα γραφής, romanized: polytonikó sýstīma grafī́s), which includes five diacritics, notates Ancient Greek phonology. The simpler monotonic orthography (Greek: μονοτονικό σύστημα γραφής, romanized: monotonikó sýstīma grafī́s), introduced in 1982, corresponds to Modern Greek phonology, and requires only two diacritics.
Polytonic orthography (from Ancient Greek πολύς (polýs) 'much, many' and τόνος (tónos) 'accent') is the standard system for Ancient Greek and Medieval Greek and includes:
acute accent (´)
circumflex accent (ˆ)
grave accent (`); these 3 accents indicate different kinds of pitch accent
rough breathing (῾) indicates the presence of the /h/ sound before a letter
smooth breathing (᾿) indicates the absence of /h/.
Since in Modern Greek the pitch accent has been replaced by a dynamic accent (stress), and /h/ was lost, most polytonic diacritics have no phonetic significance, and merely reveal the underlying Ancient Greek etymology.
Monotonic orthography (from Ancient Greek μόνος (mónos) 'single' and τόνος (tónos) 'accent') is the standard system for Modern Greek. It retains two diacritics:
single accent or tonos (΄) that indicates stress, and
diaeresis (¨), which usually indicates a hiatus but occasionally indicates a diphthong: compare modern Greek παϊδάκια (/paiˈðaca/, "lamb chops"), with a diphthong, and παιδάκια (/peˈðaca/, "little children") with a simple vowel.
A tonos and a diaeresis can be combined on a single vowel to indicate a stressed vowel after a hiatus, as in the verb ταΐζω (/taˈizo/, "I feed").
Although it is not a diacritic, the hypodiastole (comma) has in a similar way the function of a sound-changing diacritic in a handful of Greek words, principally distinguishing ό,τι (ó,ti, "whatever") from ότι (óti, "that").