This is the 604th most frequent Finnish word.
sekuntia
"Seconds" (partitive plural form of "sekunti").
Here, 'sekuntia' is used in its partitive singular form to denote an unspecified quantity of time measured in seconds, which is being asked about.
Kuinka monta sekuntia kesti juosta sata metriä?
How many seconds did it take to run a hundred meters?
'Sekuntia' here represents a measured time duration and is in the partitive singular form because it denotes a countable, specific duration of time.
Hän pystyi pitämään hengitystään vain viisi sekuntia veden alla.
He could hold his breath underwater for only five seconds.
Here, 'sekuntia' is the partitive singular form of 'sekunti', indicating the duration of time to wait.