Hacker News Reader

They are clearly not synonyms. At the very least, notice this difference in your two definitions.

1. A single data point.

2. The average of many data points

There's no single data point here. You put a thermometer in the air, it takes a finite time to take a measurement, it's actually averaging over time.

And then you record one data point. Really, if you're going to be a pedant then at least make an effort.