寝る, 寐る, ねる
Ichidan verb, Intransitive, See 眠る・1
1. to sleep (lying down)
2. to go to bed, to lie in bed
3. to lie down
4. to sleep (with someone, i.e. have intercourse)
5. to lie flat (e.g. of hair)
寝る前に歯を磨きなさい。
に
Particle
1. at (place, time), in, on, during
2. to (direction, state), toward, into
3. for (purpose)
4. because of (reason), with
5. by, from