To go into something by falling.
The cat might fall into the pool if you're not careful.
To enter a condition or state, especially a negative one.
After it closed, the old mall fell into disrepair.
To enter something (especially a profession) without having planned it.
Most of us didn't plan to be designers; we just fell into the job.
To be classified as; to fall under.
Trees fall into two main categories: deciduous and evergreen.