noun / verb
rein
RAYN/reɪn/
A guiding strap attached to an animal's bridle.
The rider holds the reins loosely as the horse walks.

Etymology
The bridle strap lets a rider guide or restrain a horse. That practical function became an image for control more generally, as in taking or holding the reins.
In context
my right rein is my direct rein it bends the horse's head controls the bend in the horse's neck
More examples
- One leather rein is twisted near the bridle.
- She reins in her horse before the sharp turn.
- We need to rein in our spending this month.
Forms
rein · reins · reined · reining