некий означает в английский

certain▼(having been determined but not specified)
determiner
[UK: ˈsɜːt.n̩] [US: ˈsɝː.tn̩]

some▼(certain, unspecified or unknown)
determiner
[UK: sʌm] [US: ˈsəm]

certain▼(not specifically named, indeterminate, indefinite)
adjective
[UK: ˈsɜːt.n̩] [US: ˈsɝː.tn̩]