Internationalization, often abbreviated as i18n (where 18 represents the number of letters between 'i' and 'n'), is the process of designing and preparing your React application so it can be adapted to various languages and regions without requiring significant engineering changes.

In a React app, internationalization involves handling:

• Different languages
• Regional formats for dates, times, numbers, and currencies
• Text direction (left-to-right or right-to-left)
• Pluralization rules
• Cultural nuances

The goal is to build a flexible application that can easily support multiple languages and regions without changing the codebase for each new language.

When you internationalize properly, localization (the actual adaptation to specific languages and cultures) becomes a straightforward task.