You’ve hit on one of the fundamental misunderstandings that bedevil this area of science…
All dimensions are abstract (i e. only exist in our collective minds). So many people struggle to differentiate between what is real and tangible (‘concrete’ nouns) and what only exists in our collective minds (‘abstract’ nouns).
We overlay reality with standardised calibration frameworks in order to calibrate and index an aspect of reality.
For example, we calibrate and index heat using the dimension of temperature. Heat is real, temperature is abstract.
We calibrate position, and relative position, using the three vectored dimension we call Space. [The word Space has (at least) two distinct meanings. Yes, it is a word that, vaguely, refers to ‘outer space’, i e.something ‘real’…though its never quute clear what].
But its meaning here, in context of dimensions, is clear. We calibrate and index [spatial] position, relative position, and changing position (motion) using the three vectored abstract dimension of Space (calibrated on standard units of miles, kilometres, inches etc etc)…the xyz axis only exists in our mind, like temperature does.
And so to Time (another word with multiple meanings). Time calibrates and indexes change and events. In the example of changing position (motion) we use, say, miles per hour to measure the rate of change. The ‘per hour’ bit is time calibrating change. And we index events using the same framework of standard units (years, days, hours etc) to reference an event..be it Big Bang (14 billion years ago) or lunch date next week (tuesday at 1).
So ALL dimensions are abstract overlays which calibrate, index and reference an underlying aspect of reality.
If people can’t simply point to what underlying aspect of reality their ‘dimension’ references, then it probably ain’t a dimension…just hectic maths.