at 
(ăt; ət when unstressed)
(ăt; ət when unstressed)prep.
Idiom: 1.
a. In or near the area occupied by; in or near the location of: at the market; at our destination.
b. In or near the position of: always at my side; at the center of the page.
2. To or toward the direction or location of, especially for a specific purpose: Questions came at us from all sides.
3. Present during; attending: at the dance.
4. Within the interval or span of: at the dinner hour; at a glance.
5. In the state or condition of: at peace with one's conscience.
6. In the activity or field of: skilled at playing chess; good at math.
7. To or using the rate, extent, or amount of; to the point of: at 30 cents a pound; at high speed; at 20 paces; at 350°F.
8. On, near, or by the time or age of: at three o'clock; at 72 years of age.
9. On account of; because of: rejoice at a victory.
10. By way of; through: exited at the rear gate.
11. In accord with; following: at my request.
12. Dependent upon: at the mercy of the court.
13. Occupied with: at work.
at it Informal
Engaged in verbal or physical conflict; arguing or fighting: The neighbors are at it again.
[Middle English, from Old English æt; see ad- in the Appendix of Indo-European roots.]