Explanation:
In the diagram, AB is adjacent to Angle"a", because if we don't consider hypotenuse, it is the only associated segment to the angle.
The segment opposite to the right angle is called Hypotenuse.
The last one, AC segment, is called the Opposite because it is the opposite to Angle"a".
If we look at it from AngleC, however, its Adjcent will be segment AC, and Opposite will be segment AB.