The
problem with this distinction is that
scientists who refer to their
observations as
data are almost never interested in a single
datum. They consider any single observation to be
decontextualized and potentially
anomalous, and look for
confirmation through
statistically-
validated
trends across large bodies of data.
Therefore, all the data together can be seen as a
unitary piece of
information, a single way to
understand the
phenomenon being studied. It's similar to the way that "story" is singular, even though one
story can contain many
subplots and
characters that are stories in their own right. I think this makes sense as the basis for a singular form of the word "data."
Also note that, at least in the
social sciences, "datum" and "data" have largely been replaced by "
data point" and "
data set,"
respectively. Perhaps that the proper argument is that "data" is plural in
Latin and
singular in
English.