This is the 12128th most frequent Russian word.
изучению
"Изучению" means "to the study" or "for studying."
Here, 'изучению' is used in the dative case as part of an expression indicating the activity of studying languages.
Он уделяет много времени изучению языков.
He dedicates a lot of time to studying languages.
In this example, 'изучению' is in the dative case, describing the purpose or focus of the referred books.
Эти книги относятся к изучению истории.
These books relate to the study of history.
Here, 'изучению' is used in the dative case to specify the activity to which the approach is directed.