Upvote:2
Well according to Wiki the answer is as below:
Pronounced [dí zǐ]
嫡子, refers to the son born in the main room. In order: the eldest son , the second son, the third son.
When there is an ordinary wife, the son of an ordinary wife is also a "diet", but the status is slightly lower than that of the son of an ordinary wife. If the regular wife has no children, then the unborn child born to the regular wife is exactly the same as the “son born to the unborn wife”. At this time, the sons born to the regular wife are called " zhengyuan ", and the sons born to the regular wife are called " pingyuan". Dizi and " bastard " relative; "heir-apparent Female" and "Shu children" relative.
嫡子 sometimes refers only to the son who inherits the family business. If there are several children in the main room, the eldest son is called the concubine, and the sons of the same mother and concubine are called concubines. In the absence of the main room, the eldest son of the concubine will also be called the concubine, and the younger brothers are still called the concubine. wikiwand
Additional Questions and Answers. Edit 1 -
(Q) This seems self contradictory „ When there is an ordinary wife, the son of an ordinary wife is also a "diet", but the status is slightly lower than that of the son of an ordinary wife“
(Q)This I can not understand: „ the unborn child born to the regular wife is exactly the same as the “son born to the unborn wife“
(A)
In Chinese ancient society , entropy wife born child is legitimate son female ; concubine wife children born as Shu children, also known as concubines children answer to question in comments
Therefore it would appear to translate to the difference being between "legitimate son" and "illegitimate son", rather than ordinary and regular.