use-icon

HOW TO USE THE DICTIONARY

Learn what the dictionary tells you about words.

Get Started Now!

Some compound words (like bus rapid transit, dog whistle, or identity theft) don’t appear on the drop-down list when you enter them into the search window. If a compound term doesn’t appear in the drop-down list, try entering the term into the search window and then hit the search button (instead of the “enter” key). Alternatively, begin searches for compound terms with a quotation mark.

use-icon

THE USAGE PANEL

The Usage Panel is a group of nearly 200 prominent scholars, creative writers, journalists, diplomats, and others in occupations requiring mastery of language. The Panelists are surveyed annually to gauge the acceptability of particular usages and grammatical constructions.

The Panelists

puzzle-icon

NEED HELP SOLVING A CROSSWORD PUZZLE?

Go to our Crossword Puzzle Solver and type in the letters that you know, and the Solver will produce a list of possible solutions.

open-icon

INTERESTED IN DICTIONARIES?

Check out the Dictionary Society of North America at http://www.dictionarysociety.com

open-icon

AMERICAN HERITAGE DICTIONARY APP

The new American Heritage Dictionary app is now available for iOS and Android.

scroll-icon

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:

Indo-European Roots

Semitic Roots

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.

open-icon

OPEN DICTIONARY PROJECT

Share your ideas for new words and new meanings of old words!

Start Sharing Now!

100-words-icon

See word lists from the best-selling 100 Words Series!

Find out more!

plat·form (plătfôrm)
Share:
n.
1.
a. A horizontal surface raised above the level of the adjacent area, as a stage for public speaking or a landing alongside railroad tracks.
b. A vessel, such as a submarine or an aircraft carrier, from which weapons can be deployed.
c. An oil platform.
2. A place, means, or opportunity for public expression of opinion: a journal that served as a platform for radical views.
3. A vestibule at the end of a railway car.
4. A formal declaration of the principles on which a group, such as a political party, makes its appeal to the public.
5.
a. A thick layer, as of leather or cork, between the inner and outer soles of a shoe, giving added height.
b. A shoe having such a construction.
6. Computers The basic technology of a computer system's hardware and software that defines how a computer is operated and determines what other kinds of software can be used.
7. Geology
a. A flat elevated portion of ground.
b. The ancient, stable, interior layer of a continental craton composed of igneous or metamorphic rocks covered by a thin layer of sedimentary rock.

[French plate-forme, diagram, from Old French : plat, flat; see PLATE + forme, form (from Latin fōrma).]

The American Heritage® Dictionary of the English Language, Fifth Edition copyright ©2017 by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
 

This website is best viewed in Chrome, Firefox, Microsoft Edge, or Safari. Some characters in pronunciations and etymologies cannot be displayed properly in Internet Explorer.