Zarka or zarqa (Hebrew: זַרְקָא֮, with variant English spellings) is a cantillation mark found in the Torah, Haftarah, and other books of the Hebrew Bible. It is usually found together with the Segol, with a Munach preceding either or both. The symbol for a Zarka is a 90 degrees rotated, inverted S. The Hebrew word זַרְקָא֮ translates into English as scatterer, since it is a scattering of notes.
Zarka is part of the Segol group. In this group, Zarka is the connector and Segol is the separator.
Zarka is also sometimes called tsinnor. Properly speaking, tsinnor is the name it receives when appears on the three poetic books (Job, Proverbs and Psalms, or the א״מת books, from their initials in Hebrew), and zarqa the name it gets on the remaining 21 books of the Hebrew Bible (also known as the prosaic books). Both sets of books use a different cantillation system.
Caution must be take not to confuse this mark with the very similar mark tsinnorit, which has the same shape but different position and use. They differ in the following:
Zarqa/tsinnor is always postpositive, which means that it is always placed after the consonant, that is, shows up to the left side: זַרְקָא֮. Tsinnorit is always centered above it: צִנּוֹרִת֘.
Zarqa/tsinnor is a distinctive cantillation symbol both on the 21 books and the 3 books, while tsinnorit appears only on the 3 books, and always combined with a second mark (merkha or mahapakh) to form a conjunctive symbol (called merkha metsunneret and mahpakh metsunnar, respectively).
Note that both marks have been wrongly named by Unicode. Zarqa/tsinnor corresponds to Unicode "Hebrew accent zinor", code point U+05AE (where "zinor" is a misspelled form for tsinnor), while tsinnorit maps to "Hebrew accent zarqa", code point U+0598.