Izhitsa (Ѵ, ѵ; Russian: И́жица) is a letter of the early Cyrillic alphabet and several later alphabets, usually the last in the row. It originates from the Greek letter ypsilon (Υ, υ) and was used in words and names derived from or via Greek, such as кѵрилъ (kürilǔ, 'Cyril') or флаѵии (flavii, 'Flavius'). It represented sounds /i/ or /v/ as normal letters и and в respectively. The Glagolitic alphabet has a corresponding letter with the same name izhitsa (Ⱛ, ⱛ). Also, izhitsa in its standard form or (mostly) in a tailed variant (similar to lowercase y) was a part of a digraph оѵ/оу representing sound /u/ (the digraph is known as Cyrillic letter Uk, and today's Cyrillic letter U originates from its simplified form).
The letter's traditional name izhitsa (ижица) is explained as a diminutive either of the word иго (igo, 'yoke'), due to the letter's shape, or of иже (izhe, 'which'), the name of the "main" Cyrillic and Glagolitic letters for the same sound /i/.
The numeral value of Cyrillic izhitsa is 400 (Glagolitic izhitsa has no numeral value). Church Slavonic editions printed in Russia use a tailed variant of the letter for the numeral purpose, whereas editions from Serbia or Romania (including books in Romanian Cyrillic alphabet), as well as early printed books from Ukraine, prefer a basic form without the tail.
Read more about Izhitsa: Russian, Serbian, (New) Church Slavonic, Romanian, Aleut, Izhitsa As A Replacement of A Different Character, Computing Codes