{ localUrl: '../page/injective_function.html', arbitalUrl: 'https://arbital.com/p/injective_function', rawJsonUrl: '../raw/4b7.json', likeableId: '3328', likeableType: 'page', myLikeValue: '0', likeCount: '1', dislikeCount: '0', likeScore: '1', individualLikes: [ 'EricBruylant' ], pageId: 'injective_function', edit: '2', editSummary: '', prevEdit: '1', currentEdit: '2', wasPublished: 'true', type: 'wiki', title: 'Injective function', clickbait: '', textLength: '1235', alias: 'injective_function', externalUrl: '', sortChildrenBy: 'likes', hasVote: 'false', voteType: '', votesAnonymous: 'false', editCreatorId: 'PatrickStevens', editCreatedAt: '2016-06-29 08:44:12', pageCreatorId: 'PatrickStevens', pageCreatedAt: '2016-06-14 19:48:02', 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: '33', text: 'A [-3jy] $f: X \\to Y$ is *injective* if it has the property that whenever $f(x) = f(y)$, it is the case that $x=y$. Given an element in the [3lm image], it came from applying $f$ to exactly one element of the [3js domain].\n\nThis concept is also commonly called being "one-to-one".\nThat can be a little misleading to someone who does not already know the term, however, because many people's natural interpretation of "one-to-one" (without otherwise having learnt the term) is that every element of the domain is matched up in a one-to-one way with *every* element of the domain, rather than simply with *some* element of the domain.\nThat is, a rather natural way of interpreting "one-to-one" is as "[499 bijective]" rather than "injective".\n\n# Examples\n\n- The function $\\mathbb{N} \\to \\mathbb{N}$ (where $\\mathbb{N}$ is the set of [-45h natural numbers]) given by $n \\mapsto n+5$ is injective: since $n+5 = m+5$ implies $n = m$. Note that this function is not [4bg surjective]: there is no natural number $k$ such that $k+5 = 2$, for instance, so $2$ is not in the range of the function.\n- The function $f: \\mathbb{N} \\to \\mathbb{N}$ given by $f(n) = 6$ for all $n$ is not injective: since $f(1) = f(2)$ but $1 \\not = 2$, for instance.', 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: [ 'function' ], commentIds: [ '4x4' ], questionIds: [], tagIds: [ 'needs_clickbait_meta_tag', 'definition_meta_tag' ], relatedIds: [], markIds: [], explanations: [], learnMore: [], requirements: [ { id: '3907', parentId: 'function', childId: 'injective_function', type: 'requirement', creatorId: 'AlexeiAndreev', createdAt: '2016-06-17 21:58:56', level: '1', isStrong: 'false', everPublished: 'true' } ], 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: '17153', pageId: 'injective_function', userId: 'EricBruylant', edit: '0', type: 'newTag', createdAt: '2016-07-19 02:21:47', auxPageId: 'needs_clickbait_meta_tag', oldSettingsValue: '', newSettingsValue: '' }, { likeableId: '0', likeableType: 'changeLog', myLikeValue: '0', likeCount: '0', dislikeCount: '0', likeScore: '0', individualLikes: [], id: '14801', pageId: 'injective_function', userId: 'PatrickStevens', edit: '2', type: 'newEdit', createdAt: '2016-06-29 08:44:12', auxPageId: '', oldSettingsValue: '', newSettingsValue: '' }, { likeableId: '0', likeableType: 'changeLog', myLikeValue: '0', likeCount: '0', dislikeCount: '0', likeScore: '0', individualLikes: [], id: '12787', pageId: 'injective_function', userId: 'PatrickStevens', edit: '1', type: 'newEdit', createdAt: '2016-06-14 19:48:02', auxPageId: '', oldSettingsValue: '', newSettingsValue: '' }, { likeableId: '0', likeableType: 'changeLog', myLikeValue: '0', likeCount: '0', dislikeCount: '0', likeScore: '0', individualLikes: [], id: '12781', pageId: 'injective_function', userId: 'PatrickStevens', edit: '1', type: 'newTag', createdAt: '2016-06-14 19:41:37', auxPageId: 'definition_meta_tag', oldSettingsValue: '', newSettingsValue: '' }, { likeableId: '0', likeableType: 'changeLog', myLikeValue: '0', likeCount: '0', dislikeCount: '0', likeScore: '0', individualLikes: [], id: '12780', pageId: 'injective_function', userId: 'PatrickStevens', edit: '1', type: 'newRequirement', createdAt: '2016-06-14 19:41:29', auxPageId: 'function', oldSettingsValue: '', newSettingsValue: '' }, { likeableId: '0', likeableType: 'changeLog', myLikeValue: '0', likeCount: '0', dislikeCount: '0', likeScore: '0', individualLikes: [], id: '12779', pageId: 'injective_function', userId: 'PatrickStevens', edit: '1', type: 'newParent', createdAt: '2016-06-14 19:41:22', auxPageId: 'function', oldSettingsValue: '', newSettingsValue: '' } ], feedSubmissions: [], searchStrings: {}, hasChildren: 'false', hasParents: 'true', redAliases: {}, improvementTagIds: [], nonMetaTagIds: [], todos: [], slowDownMap: 'null', speedUpMap: 'null', arcPageIds: 'null', contentRequests: {} }