Abduction moves a limb away from the midline of the body and adduction brings it back, so a lateral raise abducts the shoulder and a cable crossover adducts it.
The memory trick that actually sticks: adduction adds the limb back to the body. Both happen in the frontal plane.
At the hip, the abductors (gluteus medius and minimus) hold the pelvis level every time a client stands on one leg, which is every step they walk. Weak ones show as a hip that drops or a knee that dives inward on the way out of a split squat.
Direct work is cheap and worth it: two sets of 15 on a banded lateral walk or a side-lying abduction, twice a week, next to the main leg work. At the shoulder, abduction above 90 degrees needs the scapula to rotate with it, which is why a client with stiff shoulders should press from a slight incline before pressing straight overhead.