These terms are often used interchangeably, and their meaning is not always well defined or understood, even within the translation industry. However, there are differences between them.
Globalization is often used as a synonym for internationalization, but depending on how it is defined it can also refer to the internationalization and localization processes combined, or to the higher level of planning needed to enable the worldwide launch of a product, including management, marketing, financial, and legal aspects.
Internationalization refers to designing and developing products, applications and content so as to enable their adaptation to various locales. The idea is to make the localization process as easy as possible from the outset. Perhaps because it is such a long word, within the translation community internationalization is commonly shortened to I18N, where the 18 stands for the number of letters between the letters "I" and "N".
Internationalization is inherent to software development, and it is essential to remove obstacles to translation, for example, by implementing Unicode, ensuring proper display of diacritics (e.g. ä, ü, è), handling different language directions, separating translatable text strings from code, and avoiding hard-coding, concatenations, etc. It also involves planning for date and time formats, currency, sorting features, name and address formats, and other aspects relating to local linguistic and cultural preferences.
This work is generally performed by developers, not translators, although translators can and should play a role in making internationalization-related decisions.
Localization refers to adapting content to meet linguistic, cultural, legal and other requirements of a specific market, or locale. For example, this includes customization of numeric, date and time formats, currency, keyboard, sorting order, paper sizes, symbols, colors, legal requirements, and many other aspects of a translation. It may also include rethinking the logic or the design of a presentation, for example, to better suit the target culture.
Translation is the process of conveying a written source language text clearly, completely, accurately, and appropriately in a target language. This complex activity isn't limited to words, but also involves converting figures, numbers, units of measurement, date formats, forms of address, and many other aspects.
What does this mean in practical terms? Here are a couple examples:
Suppose you need a German version of a paper written in English that describes the use of satellite imagery in the forecast process. This text will need to be translated, and this will include any appropriate number/unit conversions, application of the appropriate grammar and style conventions of the target language, and perhaps adaptation of certain aspects appropriate to the conventions of the target public.
But if you were developing an instructional website that will support several languages, you will need to internationalize it in order to provide Unicode support for language-specific diacritics, provide the ability to change date formats, perhaps code it for switching among different languages, etc. During translation, the content will also need to be localized by converting units, translating or adapting images and figures, and perhaps even some icons and colors.
There is significant overlap between these concepts. Internationalization differs from translation and localization in that it is applied to the source product to enable it to support or facilitate later translation or localization. On the other hand, translation and localization refer essentially to the same concept, with localization adding some focus on specific locale issues that a translation might not take into consideration. In fact, most professional translators today will take their work into the realm of localization when they adapt and customize for their target locales. Finally, globalization encompasses all of these processes to create a globally accessible and usable product.
What about adaptation? Adaptation refers to altering something to make it suitable for some other use or activity. In our context, adaptation concerns us in two ways. First, during the process of selecting materials for a particular use, perhaps for a distance learning course, you may need to adapt them to your needs. This might involve removing some sections, adding or augmenting others, adding or modifying graphics, and perhaps changing the format used to present the original material. Second, when turning to the translation of the materials you may need to adapt them to the needs of your audience, perhaps by altering some content to local needs, such as changing a case study centered on one geographical location for another, perhaps more locally relevant.