1. smallness; small item
光の小爆発が起こり、一瞬、視界が光に満たされる。A small explosion of light occurs, and for an instant, the field of vision is filled with light.
2. short month (i.e. having fewer than 31 days)
3. urine; piss; pee; urination
4. elementary school
まあ、第三小の先生ですか。Oh, so you're a teacher at Daisan Elementary?
5. smaller (of two things, places, etc. with the same name); inferior
6. younger (of two people with the same name); junior
7. unit of field area (approx. 400 sq m)