I can't think of any examples of "pitch" meaning distance or separation. Is it because of how CRT monitors originally operated, where the rays could be measured in angle differences?
"Pitch" is used to describe the interval of a repeating pattern rather than a single dimension.
The pixel pitch or "dot pitch" is a measure of how far it is until the pixel pattern repeats itself. It's not the same as the separation, because you could have big or small pixels and different patterns. If the pixel color pattern goes RGB, then the pitch is going to be three times ( separation plus spacing). Due to manufacturing tolerances it's harder to control the exact dot size, but the interval is well controlled.
On semiconductors it is the term to describe the spacing of pins. The old 7400 TTL series from the 70's had pins with a 0.1" pitch, while the fine pitch ball grid arrays such as in your cell phone might have a connector pitch of less than a mm.
It's important to note the different dimensions of size, spacing, and pitch. In [this solder pad layout] (https://www.maximintegrated.com/en/images/appnotes/5283/5283Fig02.gif) the spacing between the pads is 0.011", the diameter (size) of the pads is 0.087" so the overall pitch is 0.0197" because the pattern repeats at that interval.
The term "pitch" is also used to describe machine screws. A fine pitch screw is one where their are many threads per inch. A standard 5 mm metric screw has a pitch of 0.8mm, but the fine pitch variant has a pitch of 0.5mm.
