This book is the first work to address the question of what kinds of words get borrowed in a systematic and comparative perspective. It studies lexical borrowing behavior on the basis of a world-wide sample of 40 languages, both major languages and minor languages, and both languages with heavy borrowing and languages with little lexical influence from other languages. The book is the result of a five-year project bringing together a unique group of specialists of many different languages and areas. The introductory chapters provide a general up-to-date introduction to language contact at the word level, as well as a presentation of the project's methodology. All the chapters are based on samples of 1000-2000 words, elicited by a uniform meaning list of 1460 meanings. The combined database, comprising over 70,000 words, is published online at the same time as the book is published. For each word, information about loanword status is given in the database, and the 40 case studies in the book describe the social and historical contact situations in detail. The final chapter draws general conclusions about what kinds of words tend to get borrowed, what kinds of word meanings are particularly resistant to borrowing, and what kinds of social contact situations lead to what kinds of borrowing situations.