A fully developed Educational Linguistics has to integrate linguistic understanding with all the areas listed above. Thus educational linguistics is inevitably a sub-branch of applied linguistics, the study of language in real-world situations where the problems and conventions are defined by non-linguists, whether the general public or language professionals such as (eg) teachers or translators. It needs to be informed by linguistic research but it cannot be limited to it, for language activity is constrained by social, economic, political and ethical factors which are beyond the immediate concerns of Linguistics proper. Thus the individual contribution that linguists can make to educational work is twofold. First, they can provide technical understanding deriving from linguistic, psycho- or socio-linguistic research to address educational problems, or to enable educational practitioners to become more proficient in addressing them themselves. Second, they can contribute by collaborating with colleagues, or by themselves operating both as linguistic and as educational researchers and teachers, understanding the inevitable "messiness" of classroom and broader educational practice, in which so many agendas are competing for attention in limited space. The first contribution is relatively easy; it is in a sense a loaning of linguistic understanding to another field. The second is more valuable, but is more difficult, and involves individuals understanding sympathetically the nature of two distinct approaches to understanding and practice.