This is the 16646th most frequent Russian word.
серийные
"Serial" or "mass-produced."
In this sentence, 'серийные' is used as an adjective to describe editions that are part of a series or serialized content.
Он купил серийные выпуски этой книги.
He purchased the serial editions of this book.
Here, 'серийные' modifies 'убийства,' describing the pattern of repeated unlawful actions performed in series.
Серийные убийства изучаются криминологами.
Serial killings are studied by criminologists.
In this context, 'серийные' describes products produced in series within industrial or manufacturing processes.