Readings & Meanings:
make certain, certain
It's necessary to ascertain whether it's true or not.
It's necessary to confirm whether it's true or not.
If you only do this to study, passing the second-level of Japanese certification will be certain.
My next job has been decided.
Ishi-hen, 石, will be our radical tonight.
The phonetic element is 隺. 隹 is a pictograph of a bird (a short and squat bird, not one with a long tail, like in 鳥). The cover 冖 adds the sense of that squat little bird flying over the horizon. A barely-visible speck in the sky.
石 is stone, of course. But think of it like a cold, hard fact. So you're investigating something hard to see and getting cold, hard facts, so as to be certain.