I think it's more common to use "data point" rather than "datum" these days. I guess it depends on whether or not you took Latin at school. - Dan Hagon

Data cannot be atomized: a single number is void without the context of the others. Hence "data is" - Egon Willighagen

@Egon - I agree a single number cannot constitute a complete dataset but not because it lacks the context of similar numbers. The real reason is the it lacks sufficent metadata to make it meaningful. If you have that you can still have a dataset with a single number - it's just likely to be very boring. I've written a fuller explanation here: http://www.danhagon.me.uk/blog... - Dan Hagon

@Dan, I'll read that post later... first reply: a number can indeed be absolute, but data in life sciences is hardly ever absolute, and the context is needed for us to understand what is going on. Think molecular similarity, or a dose of some compound (drug, toxic) which only makes sense if you know the level that is letal. - Egon Willighagen