The dictionary provides characteristics of 400 word-forming elements (prefixes and roots) of the ancient Greek and Latin languages. As illustrative examples, 1,500 foreign words existing in the Russian language are given, and - for comparison - about 1,000 terms from English, French, German and other languages; their origin and meaning are revealed. The reference dictionary allows you to find out how the birth of terms occurred and is happening, learn to understand many thousands of words. The dictionary is intended for high school students and students, teachers, journalists, as well as for everyone who needs to correctly understand and use foreign words in speech.