a. An awareness of morality in regard to one's behavior; a sense of right and wrong that urges one to act morally: Let your conscience be your guide.
b. A source of moral or ethical judgment or pronouncement: a document that serves as the nation's conscience.
c. Conformity to one's own sense of right conduct: a person of unflagging conscience.
2. The part of the superego in psychoanalysis that judges the ethical nature of one's actions and thoughts and then transmits such determinations to the ego for consideration.
3. Obsolete Consciousness or awareness of something.
in (all good) conscience
In all fairness; by any reasonable standard.
on (one's) conscience
Causing one to feel guilty or uneasy.
[Middle English, from Old French, from Latin cōnscientia, from cōnsciēns, cōnscient-, present participle of cōnscīre, to be conscious of : com-, intensive pref.; see COM- + scīre, to know; see skei- in the Appendix of Indo-European roots.]
The American Heritage® Dictionary of the English Language, Fifth Edition copyright ©2018 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.