- Absolutely essential. See Synonyms at indispensable. (adjective)
- Needed to achieve a certain result or effect; requisite: the necessary tools. (adjective)
- Unavoidably determined by prior conditions or circumstances; inevitable: the necessary results of overindulgence. (adjective)
- Logically inevitable. (adjective)
- Required by obligation, compulsion, or convention: made the necessary apologies. (adjective)
American Heritage(R) Dictionary of the English Language, Fifth Edition. Copyright (c) 2011 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.