Ichidan/ru-verb

1. to become known; to come to light; to be discovered
2. to be known; to be understood (usu. in the negative)
3. to clearly not amount to much; to be insignificant
4. to be evident; to be obvious; to go without saying (as 知れたこと)
5. to be very intense (of worry, hope, etc.); to be severe (as どんなに…か知れない, どれほど...か知れない, etc.)