Inge and other participants provided us with several definitions on mobile learning, but still everyone has a bit of their own understanding of the term based on personal experience. This is my attempt to define mlearning for my own goals.
First of all we must to remember that every definition has its goal. A definition helps us to see a problem under the right angle. First question is "What problem?" Next question is "What definition will be helpful?" Let the problem will be how to easily distinguish the mobile learning from other types of learning in relation to its instrument (whether it's digital or not).
What if we define mobile learning simply as any type of learning that is mediated with personal digital device which is associated with learner and can be brought anywhere? Any type of activity is learning (Halperin), and mobile devices helps us to empower the learning component of our activities. Also network connection is important, but isn't crucial.
In general, I don't need any special device to learn something. I learn anytime when I do something. But conscious (intentional) learning needs mediation device, and when it's digital we talking about elearning. The most interesting thing here: as we make our devices more mobile and ubiquitous, our learning can be less conscious and less formal, but still mediated. This leads to empowering of the learning in almost every type of activities.