Try sensing something that isn't a relationship.
This seems easy enough. There is no shortage of things we sense that don't appear to be relationships.
The existence of 'distance' is about as self evident as we can get.
What is distance?
We experience a sense of distance pretty much all the time. The idea of dimensions (structured distance) is so obvious that they are assumed in mathematics and physics. Explaining distance is as unnecessary as explaining water to a fish or air to a human...
What can we say about distance?
We can measure distance. Measuring distance generally takes the form of taking another known distance (a ruler) and comparing to the first distance. We measure one distance by its relationship to another distance. This tells us how the two distances compare - but it doesn't tell us anything about, for example, what creates distance. The distances have to already exist before we can compare them. Measuring distances doesn't tell us how to create new distances.
Another way of expressing distances is in the form of equations. E.g. distance = velocity x time.
This particular equation describes the existence of a relationship between 'distance', 'velocity' and 'time'. This doesn't reveal to us what makes time either.
The relationship exists - but it doesn't tell us much about the objects being related beyond the existence of those relationships.
No matter how we try to quantify, measure, describe, define or otherwise state properties of 'distance', the only meaningful statements we can make are descriptions of the various relationships that distance has.
The length of your thumb is long or short compared to your fingers, or your toes, or your forearm. The metre is defined as 1/10000 of the distance from the north pole to the equator through Paris (or the distance light travels in 1/299,792,458 seconds).