This paper investigated the corresponding relationships between

wuji

（无极），

taiji

（太极），

yin

-

yang

（阴阳） and certain mathematical concepts， i.e.

wuji

directly corresponds to the empty set， the number 0 and the intial origin；

taiji

corresponds to the universe set， the number 1 and the unit circle；

yin

-

yang

directly corresponds to the binary opposition division of universe set， the combination of numbers or characters 0 and 1， and the binary division of unit circle （into upper and lower semicircles， or left and right semicircles）. In addition， the definitions of set descrication， set partitioning， and the set of basic equations （in a generalised sense） for

yin

and

yang

were given. The relationships between two set equations

<math id="M2"><mi>A</mi><mo>⋂</mo><mi>B</mi><mo>=</mo><mi mathvariant="normal">∅</mi><mo>

</mo><mtext> </mtext><mi>A</mi><mo>⋃</mo><mi>B</mi><mo>=</mo><mi>I</mi><mtext>  </mtext></math>

https://html.publish.founderss.cn/rc-pub/api/common/picture?pictureId=99747431&type=

https://html.publish.founderss.cn/rc-pub/api/common/picture?pictureId=99748307&type=

38.60800171

3.30200005

and unity of opposites were discussed， and the relationships between

yin

-

yang

sets and mutual complementary sets， oppositional events of

yin

and

yang

were explored. The basic properties of

yin

-

yang

sets are illustrated by the definition of

yin

-

yang

set partitioning， so as to reveal the basic laws of

yin

-

yang

transformation.