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.^[1] Usually, only several out of the 15 variant components are listed under radical 乛 in dictionary indexes.

• Oracle bone script character
• Bronze script character
• Large seal script character
• Small seal script character

In the Unihan Database, 亀 (Japanese simplified form of 龜) falls under Radical 5 + 10 strokes, while other variants of 龜 (including Simplified Chinese 龟) fall under Radical 213 (龜 "turtle"), causing an inconsistency. However, in most Japanese dictionaries, 亀 is treated as a variant of Radical 213 (龜) and indexed Radical 213 + 0 strokes.

As an independent character it is a Jōyō kanji, or a kanji used in writing the Japanese language. It is a secondary school kanji.^[2] It is also used in the Chinese language.

It means "secondary" and is mainly used in compounds.

• List of jōyō kanji