So datum would be a singular piece of data. But it gets confusing and varies based on what you’re talking about. If you have a database filled with n files, each having m ints, then you can say that each of these files is a datum of that database, but at the same time, each of these datum is data; with each of the ints being datum. But then each of the ints had multiple bits, so the ints themselves are data. So it depends which level you’re talking about.
You’ll probably hate this, but my relevant take: “data” can be singular and using it as plural sounds wrong.
So datum would be a singular piece of data. But it gets confusing and varies based on what you’re talking about. If you have a database filled with n files, each having m ints, then you can say that each of these files is a datum of that database, but at the same time, each of these datum is data; with each of the ints being datum. But then each of the ints had multiple bits, so the ints themselves are data. So it depends which level you’re talking about.
The only datum I can think of is tidal datum, used in shoreline measurements. I’ve seen the plural given as datums though… argh!