be ... years sb's junior | be sb's junior (by ... )
to be younger than sb, by the number of years mentioned :
She's four years his junior.
She's his junior by four years.
be ... years sb's junior | be sb's junior (by ... )
to be younger than sb, by the number of years mentioned :
She's four years his junior.
She's his junior by four years.
Oxford Advanced Learner's English Dictionary. Оксфордский английский словарь для изучающик язык на продвинутом уровне. 2005