1. The Gemini - - Gemini's mark symbol twin, compares in the first two marks, has been abstract a point; 双子座——双子座的符号象徵双胞胎，相较于前两个符号，就比较抽象了一点；
2. Dizygotic twins - Twins born from the simultaneous fertilization of two different eggs by two different sperm. 双卵双胞胎 -双城同时出生的两个不同的施肥鸡蛋由两个不同的精子。
3. Dizygotic twins - Twins born from the simultaneous fertilization of two different eggs by two different sperm. 双卵双胞胎 -双城同时出生的两个不同的施肥鸡蛋由两个不同的精子。
4. There are different direction twins in its casting structures, and parallel second twins emerge in one big twin where micro cracks appear along twin boundary. 铸态组织中存在不同位向的孪晶，大孪晶中有许多平行的二次孪晶，沿孪晶界诱发微裂纹；
5. And there is twin dynamic recrystallization in the HERT process. The twins and secondary twins can hinder the spreading of cracks. 变形过程发生了孪生动态再结晶，孪晶和二次孪晶的产生可以阻碍裂纹扩展，镁在基面滑移与孪生的交互作用下形成微晶和孪晶位错；
