This character is a Other Letter and is mainly used in the Han script. The Unihan Database defines it as second; 2nd heavenly stem. Its Pīnyīn pronunciation is yǐ.
The glyph is not a composition. Its East Asian Width is wide. In bidirectional text it is written from left to right. When changing direction it is not mirrored. U+4E59 offers a line break opportunity at its position, except in some numeric contexts. The glyph can be confused with 2 other glyphs.
The Wikipedia has the following information about this codepoint:
Radical 5 or radical second (乙部), meaning "second", is one of 6 of the 214 Kangxi radicals that are composed of only one stroke. However, this radical is mainly used to categorize miscellaneous characters otherwise not belonging to any radical, mainly featuring a hook or fold, and 乙 is the character with the least amount of strokes.
In the ancient Chinese cyclic character numeral system, 乙 represents the second Celestial stem (天干 tiāngān).
In the Kangxi Dictionary, there are 42 characters (out of 49,030) to be found under this radical.
In mainland China, 乙 along with other 14 associated indexing components, including 乚, etc., are affiliated to a new radical 乛 (乛部), which is the 5th principal indexing component in the Table of Indexing Chinese Character Components predominantly adopted by Simplified Chinese dictionaries. Usually, only several out of the 15 variant components are listed under radical 乛 in dictionary indexes.