Earlier definitions of mobile learning focused on the technology (the provision of training on PDAs, smartphones, mobile devices). Later, the definition of mobile learning evolved to focus on mobility (any learning that happens when the learner is not in a fixed place), then learning (the acquisition of knowledge and skills through mobile devices). Whether we can define it consistently, whether we can afford it, or whether we can support it—the bottom line is that mobile learning is not going away. This excerpt from  TD at Work “Applying Learning Theory to Mobile Learning” looks at the drivers and barriers affecting mobile learning adoption.