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In Unicode, two glyphs are Z variants of each other (usually spelled zVariants) if they share the same etymology, but have slightly different appearances and Unicode character encodings. For example, the Unicode characters U+8AAA and U+8AAC are Z variants of each other. The concept of the Z variant is only applicable to " CJKV script" (Chinese, Japanese, Korean and Vietnamese), the subtitle of the unified ideogram of CJKV.
1. Differences on the Z axis
The assignment of CJK's unicode encoding is organized through three "axes". The X-axis represents semantic differences; for example, the Latin capital letter A (U+0041A) and the capital letter of the Greek letter alpha (U+0391A) are represented in Unicode by two different encodings, called "X variants" ( although the term is uncommon). The Y-axis represents significant differences in appearance, but not semantics; for example, the traditional character "cat" (u+8c93 cat) and the simplified character (u+732b cat) are Y variants of each other.
The Z-axis represents minor printing variance. For example, the Chinese characters (U+838A Zhuang) and (U+8358 単) are Z variants, as are (U+8AAA Say) and (U+8AAC Say) are Z variants. Unicode.org's glossary defines "Z-variant" as "two CJK unified ideographs with the same semantics and uniform shape", or in the CJKV unified ideograph.
Suffice it to say that if the CJK unified ideograms were perfectly "unified", the Z variant would not have appeared either. It appeared to help text "round-trip" between Unicode and other CJK encodings - such as Big5 and CCCII. For example, the CCCII code of the character "Zhuang" is 21552D, while its Z variant "単" has the CCCII code 2D552D. These two variants are given different Unicode codes, so the text can be converted between CCCII codes and Unicode codes losslessly.
2. Doubt
There is some confusion about the exact definition of "Z variant". For example, in a 2002 Internet-Draft ( RFC 3743 ), (U+4E0D not) and (U+F967 not) were defined as "font variants", while (U+5154 in Mandarin) Rabbit) and Japanese (U+514E 兎) - both semantically "rabbit" - are both considered Z variants by the Unicode Consortium's Chinese Character Database.