Consider this image:
Wikipedia calls the red line a "dotted line". However, the Wikipedia page is one of the search results for "dashed line". Which term would I use?
In terms of "dotted line" or "dashed line", what should I call the black line, opposed to the others? Just a "line"?
How about the blue one? Could someone please give me a hint?
These line patterns are commonly used in statistical charts and graphs and are called:
The other kind of line featuring only dashes ( - - - - - ) but not shown in your post would be a dashed line.
See source.
Here is one source used in academia:
Source: https://tex.stackexchange.com/questions/45275/tikz-get-values-for-predefined-dash-patterns
Ditto @Astralbee. Let me just add:
"Solid line" means a line with no breaks. Like if you were drawing it with a pencil, you'd put the pencil down and draw without picking it up.
"Dotted line" means, as the name implies, a line made up of dots. To draw it you would make a dot with a pencil, move the pencil a little and make another dot, etc.
"Dashed line" means a line made up of short strokes with breaks in between. You would put the pencil down, draw a short distance, pick it up and move it just a little, then put it down and draw another short stroke, etc.
I don't think there is a generally-recognized names for patterns like #3. I'd say "a line with alternating dots and dashes". Admittedly a long and cumbersome phrase. If someone said a "dash-dotted line" like Astralbee suggests I might figure out what he meant, but as I say, I don't think that's an agreed-upon term that every English speaker would recognize.
Also commonly used for the third case is dash-dot line (as well as dash-dotted and rarely dashed-dotted). The order is sometimes reversed ("dot-dashed"), so it should be clear that there's no single universally correct answer. Here are some examples of actual usage.
Note that "dashed and dotted" (as mentioned in the comments) is never (IME) used for these lines. There's a good reason for this. A typical usage in a figure caption is "Samples A, B, and C are denoted by solid, dashed, and dash-dot(ted) lines respectively". Replace "dash-dotted" with "dashed and dotted" and you get a sentence that's harder to parse, and on first reading implies a mismatch between the number of samples and the number of lines.
It's also not uncommon in academic papers to refer to short-dashed and long-dashed lines (the hyphen being important as the length modifies the "dash" not the "dashed line"). While it would be possible to describe an arbitrary pattern of short and long dashes and dots, once the simple set of solid, long-dashed, dotted, short-dashed, and dash-dot lines is exhausted in a graph it's better to refer to them graphically either in the caption or a legend. By the way, to preempt comments, there's still a use for these as figures generally work better if they don't rely solely on colour (to account for monochrome printers and colourblind readers). In technical drawings (as opposed to graphs), lines may well be referred to by their meanings rather than their types, except to define meanings for the various line types used.
