Aristarchian symbols are editorial marks developed during the Hellenistic period and the early Roman empire for annotating then-ancient Greek texts—mainly the works of Homer. They were used to highlight missing text, text which was discrepant between sources, and text which appeared in the wrong place.
Two main types of ancient Greek philological annotations can be distinguished: signs and explicit notes. Aristarchian symbols are signs.
The first philological sign (σημεῖον) invented by Zenodotos of Ephesos, the first head of the Alexandrinian Library, in his edition of Homer was the obelos (ὀβελός, a short horizontal dash ), which Zenodotos used to mark spurious lines. For this reason, the practice of using signs for textual criticism has been called 'obelism'.
Aristophanes of Byzantium invented later the 'asterisk' (ἀστερίσκος) to mark lines that are duplicated from another place, as well as the 'lunate sigma' (σίγμα) and the 'antisigma' (ἀντίσιγμα) for two consecutive and interchangeable lines of the same content.
A system of dots also credited to Aristophanes of Byzantium was developed in the 3rd century BCE. A hypostigme ('low dot') marked an occasion for a short breath after a short phrase, a stigme mese ('middot') (στιγμή) marked an occasion for a longer breath after a longer passage, and a stigme teleia ('high dot') marked a full stop at the end of a completed thought. Other writers employed two dot punctuation to mark the ends of sentences or changing speakers. Less often, arrangements of three , four , and five dots appeared.
The number of the philological signs and in some cases their meanings were modified by Aristarchos of Samothrake (220–143 BCE), sixth head of the Alexandrinian Library. He used critical and exegetical signs in his editions of the Homeric poems.
A 'dotted lunate sigma' (σίγμα περιεστιγμένον) was used by him as an editorial sign indicating that the line so-marked is at an incorrect position in the surrounding text; an antisigma, or 'reversed lunate sigma' , may also mark an out of place line. A 'dotted antisigma' or 'dotted reversed sigma' (ἀντίσιγμα περιεστιγμένον) indicates the line after which rearrangements should be made, or to variant readings of uncertain priority.
The diple marked lines whose language or content was perhaps also exegetically noteworthy and pointed to a corresponding explanation in a commentary. The diple periestigmene (διπλῆ περιεστιγμένη) a dotted diple pointed to a verse in which Aristarchos' edition differs from that of Zenodotos. He used the obelos added to the asteriskos where the repeated line is out of place and the stigme (στιγμή) indicated suspected spuriousness.
Aristarchos's semeia were adopted early on by scholars in Rome, and became the standard philological signs for centuries to follow. Some papyrus fragments contain un-Aristarchian signs whose use was fairly consistent nevertheless. For instance, the so-called ancora, an anchor-shaped diagonal upward and downward pointer or , often marks places where text had been omitted or draws attention to text-critical restoration in the top or bottom margin, respectively.
In addition to no punctuation, many original source texts in ancient Greek were written as an unbroken stream of letters, with no separation between words. The hypodiastole, a curved, comma-like mark , was used to disambiguate certain homonyms and marked the word-break in a sequence of letters that should be understood as two separate words. Its companion mark, the enotikon (ἐνωτικόν) , served to show that a sequence of letters which might otherwise be read as two separate words, should instead be read as a single word. The paragraphos (see picture, right) marked a division in a text. The coronis was used to mark the ends of entire works, or the end of major sections in poetic and prose texts.