1. A line that establishes or marks a border.
2. An indefinite area intermediate between two qualities or conditions: The borderline between love and hate is often thin.
3. Informal A person with borderline personality disorder.
a. Verging on a given quality or condition: borderline poverty.
b. Of a questionable nature or quality: an applicant with borderline qualifications.
2. Psychiatry Of, related to, or having borderline personality disorder.
The American Heritage® Dictionary of the English Language, Fifth Edition copyright ©2020 by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
Indo-European & Semitic Roots Appendices
Thousands of entries in the dictionary include etymologies that trace their origins back to reconstructed proto-languages. You can obtain more information about these forms in our online appendices:
The Indo-European appendix covers nearly half of the Indo-European roots that have left their mark on English words. A more complete treatment of Indo-European roots and the English words derived from them is available in our Dictionary of Indo-European Roots.