Most definitions emphasize that online learning is delivered through Internet or web-based mediums (Moore et al., 2010; Ryan and Young, 2015; Lee, 2017).

It is common to define online learning as where the majority of teaching is performed online. For example, the Instructional Technology Council (ITC), which is affiliated with the American Association of Community Colleges (AACC), 

defines online learning as where at least 80 percent of instruction is delivered online.

Here online learning is defined simply as:

'Education that is provided over the Internet.'

Rarely is teaching done exclusively using the Internet or Web. The extent the Internet is used , or that distance learning is provided varies. Thus a scale of use can be seen, ranging from teaching and learning being done entirely online, right down to the Internet simply being used as an adjunct to teaching, with most learning being done in a face-to-face manner.