“结婚适龄”常见的英文表达是 “of marriageable age” 。
例如：
In many cultures, people are expected to marry when they are of marriageable age.（在许多文化中，人们被期望在结婚适龄时结婚。）
此外，也可以用 “at a suitable age for marriage” 来表达类似意思。例如：
She's at a suitable age for marriage, but she hasn't found the right person yet.（她到了结婚适龄，但还没找到合适的人。）