{ localUrl: '../page/unit_ring_theory.html', arbitalUrl: 'https://arbital.com/p/unit_ring_theory', rawJsonUrl: '../raw/5mg.json', likeableId: '0', likeableType: 'page', myLikeValue: '0', likeCount: '0', dislikeCount: '0', likeScore: '0', individualLikes: [], pageId: 'unit_ring_theory', edit: '1', editSummary: '', prevEdit: '0', currentEdit: '1', wasPublished: 'true', type: 'wiki', title: 'Unit (ring theory)', clickbait: 'A unit in a ring is just an element with a multiplicative inverse.', textLength: '1305', alias: 'unit_ring_theory', externalUrl: '', sortChildrenBy: 'likes', hasVote: 'false', voteType: '', votesAnonymous: 'false', editCreatorId: 'PatrickStevens', editCreatedAt: '2016-07-28 15:12:05', pageCreatorId: 'PatrickStevens', pageCreatedAt: '2016-07-28 15:12:05', seeDomainId: '0', editDomainId: 'AlexeiAndreev', submitToDomainId: '0', isAutosave: 'false', isSnapshot: 'false', isLiveEdit: 'true', isMinorEdit: 'false', indirectTeacher: 'false', todoCount: '0', isEditorComment: 'false', isApprovedComment: 'true', isResolved: 'false', snapshotText: '', anchorContext: '', anchorText: '', anchorOffset: '0', mergedInto: '', isDeleted: 'false', viewCount: '41', text: '[summary: A unit of a [3gq ring] is an element with a multiplicative inverse.]\n\nAn element $x$ of a non-trivial [3gq ring]%%note:That is, a ring in which $0 \\not = 1$; equivalently, a ring with more than one element.%% is known as a **unit** if it has a multiplicative inverse: that is, if there is $y$ such that $xy = 1$.\n(We specified that the ring be non-trivial. \nIf the ring is trivial then $0=1$ and so the requirement is the same as $xy = 0$; this means $0$ is actually invertible in this ring, since its inverse is $0$: we have $0 \\times 0 = 0 = 1$.)\n\n$0$ is never a unit, because $0 \\times y = 0$ is never equal to $1$ for any $y$ (since we specified that the ring be non-trivial).\n\nIf every nonzero element of a ring is a unit, then we say the ring is a [481 field].\n\nNote that if $x$ is a unit, then it has a *unique* inverse; the proof is an exercise.\n%%hidden(Proof):\nIf $xy = xz = 1$, then $zxy = z$ (by multiplying both sides of $xy=1$ by $z$) and so $y = z$ (by using $zx = 1$).\n%%\n\n# Examples\n\n- In [48l $\\mathbb{Z}$], $1$ and $-1$ are both units, since $1 \\times 1 = 1$ and $-1 \\times -1 = 1$. However, $2$ is not a unit, since there is no integer $x$ such that $2x=1$. In fact, the *only* units are $\\pm 1$.\n- [4zq $\\mathbb{Q}$] is a [481 field], so every rational except $0$ is a unit.', metaText: '', isTextLoaded: 'true', isSubscribedToDiscussion: 'false', isSubscribedToUser: 'false', isSubscribedAsMaintainer: 'false', discussionSubscriberCount: '1', maintainerCount: '1', userSubscriberCount: '0', lastVisit: '', hasDraft: 'false', votes: [], voteSummary: 'null', muVoteSummary: '0', voteScaling: '0', currentUserVote: '-2', voteCount: '0', lockedVoteType: '', maxEditEver: '0', redLinkCount: '0', lockedBy: '', lockedUntil: '', nextPageId: '', prevPageId: '', usedAsMastery: 'false', proposalEditNum: '0', permissions: { edit: { has: 'false', reason: 'You don't have domain permission to edit this page' }, proposeEdit: { has: 'true', reason: '' }, delete: { has: 'false', reason: 'You don't have domain permission to delete this page' }, comment: { has: 'false', reason: 'You can't comment in this domain because you are not a member' }, proposeComment: { has: 'true', reason: '' } }, summaries: {}, creatorIds: [ 'PatrickStevens' ], childIds: [], parentIds: [ 'algebraic_ring' ], commentIds: [], questionIds: [], tagIds: [], relatedIds: [], markIds: [], explanations: [], learnMore: [], requirements: [], subjects: [], lenses: [], lensParentId: '', pathPages: [], learnMoreTaughtMap: {}, learnMoreCoveredMap: {}, learnMoreRequiredMap: {}, editHistory: {}, domainSubmissions: {}, answers: [], answerCount: '0', commentCount: '0', newCommentCount: '0', linkedMarkCount: '0', changeLogs: [ { likeableId: '0', likeableType: 'changeLog', myLikeValue: '0', likeCount: '0', dislikeCount: '0', likeScore: '0', individualLikes: [], id: '17645', pageId: 'unit_ring_theory', userId: 'PatrickStevens', edit: '0', type: 'newParent', createdAt: '2016-07-28 15:12:06', auxPageId: 'algebraic_ring', oldSettingsValue: '', newSettingsValue: '' }, { likeableId: '0', likeableType: 'changeLog', myLikeValue: '0', likeCount: '0', dislikeCount: '0', likeScore: '0', individualLikes: [], id: '17643', pageId: 'unit_ring_theory', userId: 'PatrickStevens', edit: '1', type: 'newEdit', createdAt: '2016-07-28 15:12:05', auxPageId: '', oldSettingsValue: '', newSettingsValue: '' } ], feedSubmissions: [], searchStrings: {}, hasChildren: 'false', hasParents: 'true', redAliases: {}, improvementTagIds: [], nonMetaTagIds: [], todos: [], slowDownMap: 'null', speedUpMap: 'null', arcPageIds: 'null', contentRequests: {} }