In my professional and academic writing experience, I have never encountered a style guide that defines rules for these words.
I am Australian, an engineer (former) and a mathematics teacher and I consider the following to be best practice when writing and teaching.
- graph – when a line is drawn (of a function/formula or of continuous data).
- chart – when other shapes and symbols (e.g. bars) are used to represent data.
- plot – when points are marked on a coordinate system.
- bar chart
- pie chart
- line graph
- scatter plot
I “teach” this but wouldn’t enforce it.
The etymology of the suffix -graph supports my practice. Scratching with a stick produces a line. But could also produce a pictograph, figure, diagram etc.
The etymology of both chart might support my practice, in that it is derived from words meaning “map”. A map is a pictorial or symbolic representation.
The etymology of plot might support my practice. Areas of land are typically divided into square or rectangular “plots”. Rectangular areas correlate with the notion of coordinates (sides of a rectangle). Furthermore, variations of plot in other languages typically mean marking points on a chart.
Other supportive uses…
- A seismograph graphs continuous earthquake data.
- A navigator plots a course on a nautical chart/map using a parallel plotter.
- A phonograph produces sound when a needle (stylus) traces over the continuous etch on the cylinder.
The word photograph seems to deviate, unless you imagine that it’s a new way to “draw” with light, the old way being with a pencil on paper.