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This new edition offers newly updated terms, and provides the latest research on word origins and meanings, with guidelines on accurate usage.
Editor(s): Editors of the American Heritage Dictionaries
Edition: 6th
Articles: 94,107
Images: 4,330
Audio files: 69,315
People: 305


Special Contributors and Consultants
Editorial and Production Staff
The Usage Panel
Usage in The American Heritage Dictionary
Variation and Change in Our Living Language
Guide to Appendix I
Guide to The Semetic Roots (Appendix II)
Appendix I: Indo-European Roots
Indo-European and the Indo-Europeans
Appendix II: Roots


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  Elementary; basic: You should never leave your baby alone in the bathtub—that's just parenting 101.   [From the common use of the number 1


24-7   Continuously; unceasingly.   [Short for 24 hours a day, 7 days a week.]


3D   Three-dimensional.   n.   A three-dimensional medium, display, or performance, especially a cinematic or graphic medium in three dim

3D printer

  A computer-controlled device that is capable of fabricating three-dimensional objects, as by extruding layers of plastic from a robotically con


401(k)   A retirement investment plan that allows an employee to put a percentage of earned wages into a tax-deferred investment account selected


411   Information or knowledge, especially when acquired by word of mouth.   [From 411, a telephone number for telephone directory informatio

4-H Club

4-H Club   A youth organization sponsored by the Department of Agriculture and offering instruction in agriculture, home economics, and other fie


  four-wheel drive


  A stimulant, C7H7N4O2Cl, that is used to form a salt with certain pharmaceutical drugs, such as diphenhydramine.   [8-, conventional numbe


9/11   September 11, 2001, the date on which two hijacked airliners were flown into the World Trade Center in New York City and another into the


1. accusative 2. Games ace 3. across 4. adenine 5. alto 6. ampere 7. or Å angstrom 8. answer 9. area 10. Spor


1. acre 2. adjective 3. Latin anno (in the year) 4. Latin annus (year) 5. anode 6. Latin ante (before) 7. anterior

a- 1

  Without; not: amoral.   [Greek; see ne in the Appendix of Indo-European roots.]

a 1

a 1 1. The first letter of the modern English alphabet. 2. Any of the speech sounds represented by the letter a. 3. The first in a series


  airman first class