font-weight对应关系

[iulo]

100 - Thin
200 - Extra Light (Ultra Light)
300 - Light
400 - Regular (Normal、Book、Roman)
500 - Medium
600 - Semi Bold (Demi Bold)
700 - Bold
800 - Extra Bold (Ultra Bold)
900 - Black (Heavy)

https://aotu.io/notes/2016/11/08/css3fontweight/index.html
https://www.w3.org/html/ig/zh/wiki/CSS3%E5%AD%97%E4%BD%93%E6%A8%A1%E5%9D%97#.E5.AD.97.E4.BD.93.E7.B2.97.E7.BB.86.EF.BC.9A.E2.80.98font-weight.E2.80.99.E5.B1.9E.E6.80.A7
https://zh.wikipedia.org/wiki/Roboto