Apprehension (noun)

1. Anxiety or fear that something bad or unpleasant will happen.
2. The act of arresting someone for a crime.
3. The ability to understand something.
4. The act of perceiving or noticing something.

Origin:

From middle english appre(h)ensioun, from old french aprehension, from latin apprehensio, from apprehendere.

Examples:

1. I felt a sense of apprehension as I approached the door.
2. The suspect was taken into custody without apprehension.
3. The book's complexity requires a level of apprehension that not all readers possess.
4. The officer's apprehension of the suspect's behavior led to further investigation.