Arbital features

rewrite summary


A page is the pri­mary build­ing block in Ar­bital. Most pages fall within one of these cat­e­gories:

All pages in the math do­main are “wiki” type pages, mean­ing they are open to pub­lic for pro­posed ed­its.

Par­ents, chil­dren, and the page hierarchy

Ar­bital pages have many kinds of con­nec­tions, par­ent-child re­la­tion­ship be­ing the strongest one. Each page can have mul­ti­ple chil­dren and mul­ti­ple par­ents, though one par­ent is most com­mon. The re­la­tion­ship im­plies that the child page is a crit­i­cal com­po­nent of the par­ent, or that the par­ent is the sum of its chil­dren. Th­ese re­la­tion­ships cre­ate a page hi­er­ar­chy, which makes ex­plain­ing, learn­ing, and dis­cov­er­ing eas­ier.

Ex­am­ple: a Chem­istry text­book will have its own Ar­bital page. Its chil­dren will be pages cor­re­spond­ing to differ­ent chap­ters. Their chil­dren will be pages cor­re­spond­ing to differ­ent sec­tions. Their chil­dren will be pages cor­re­spond­ing to home­work prob­lems, ex­per­i­ments, or ex­tra ma­te­rial. Each sub­page is a crit­i­cal com­po­nent that makes the en­tire book work well.

Ex­am­ple: Ad­di­tion, sub­trac­tion, mul­ti­pli­ca­tion and di­vi­sion pages are all chil­dren of ar­ith­metic. We can say that ar­ith­metic is “ad­di­tion, sub­trac­tion, mul­ti­pli­ca­tion, and di­vi­sion.”


Aside from the par­ent-child re­la­tion­ship, pages can also have tags. Th­ese are similar to stan­dard #hash­tags, but each tag ac­tu­ally points to an Ar­bital page. Tags cre­ate more loose con­nec­tions, im­ply­ing that the page is talk­ing about the tag, per­haps in­di­rectly.

Ex­am­ple: A re­view of the Chem­istry book wouldn’t be a child of the Chem­istry book page. In­stead, it would be tagged with the Chem­istry book page.


To sim­plify each page the au­thor(s) will as­sume that the reader already un­der­stands cer­tain top­ics. Th­ese as­sump­tions will be listed in the req­ui­site sec­tion. While you can ig­nore them and con­tinue read­ing, if the ma­te­rial is difficult or un­clear, it’s likely be­cause you don’t un­der­stand one of the con­cepts a page re­lies on. How­ever, if you’ve met all the re­quire­ments, you can ask a ques­tion or sug­gest a re­quire­ment.

For this rea­son, ev­ery page has a sec­tion at the bot­tom where you can mark that you un­der­stand that page. Ar­bital will re­mem­ber it and ac­count for it when check­ing if you meet the re­quire­ments on other pages.

Ex­am­ple: a page on in­te­grals will have the page on deriva­tives as one re­quire­ment among oth­ers.


Lenses are al­ter­nate tabs on a page which ex­plain the same con­cept, but from differ­ent per­spec­tives or with a differ­ent set of req­ui­sites. If you don’t meet re­quire­ments for the pri­mary page, but still need to get a quick un­der­stand­ing, you can check out a lens, which will usu­ally be writ­ten in a more ac­cessible man­ner.

Ex­am­ple: the pri­mary page on Deriva­tives will be talk­ing about the con­cept us­ing “limits” and com­plex math no­ta­tions, whereas a lens can de­scribe the same con­cept us­ing the “tan­gent” con­cept and em­ploy­ing lots of pic­tures.

You can hover over any link that goes to an Ar­bital page to see the sum­mary of that page, along with other in­for­ma­tion. This by it­self might an­swer some ques­tions you have, and will very likely help you see if that page is what you are look­ing for. If the page has any lenses, they will ap­pear in the popover as well, so you can choose the sum­mary that works for you.


Most pages have com­ments, where the read­ers dis­cuss the con­tents of the page and re­lated top­ics. The com­ments are or­ga­nized in two tiers: top-level com­ments and replies to them. For this rea­son, if you have mul­ti­ple points to make, please make each of them a sep­a­rate com­ment. This way all the replies to each com­ment will be on that topic.

When you hover over a para­graph, you have the op­tion of cre­at­ing an in­line com­ment, which will be at­tached to the se­lected text. This makes it more clear for other read­ers what you are refer­ring to, and gives them the con­text to un­der­stand your com­ment or ques­tion.

Some­times a page will have the com­ments dis­abled or re­stricted to make sure the qual­ity of the con­ver­sa­tion is high.

Ques­tions and answers

If some­thing is not clear to you, you can ask a ques­tion. This will cre­ate a new page, where you can also see all the an­swers. The func­tion­al­ity is very similar to Stack­Ex­change-type web­sites.

When you type up a ques­tion, you will see a list of other similar ques­tions that have been asked. Please take a look to see if your ques­tion has already been asked and an­swered. Once you sub­mit the ques­tion, users who are sub­scribed to the page will be no­tified, and one of them is likely to re­spond.


You can like any page or com­ment. Lik­ing will help the page’s visi­bil­ity, it will show up higher in search re­sults, and the au­thor(s) of the page will get karma.

Please note that lik­ing a page is not at all the same as agree­ing with the page. (See the Votes sec­tion for that.) Lik­ing means you find the page valuable, and you think it does its job well: a page about a spe­cific con­cept pre­sents it clearly and con­cisely; a page about some area pro­vides a com­pre­hen­sive cov­er­age, while high­light­ing im­por­tant de­tails; a lens pre­sents the same con­cept from a differ­ent an­gle, while re­tain­ing ac­cu­racy and be­ing up to date; a ques­tion is well writ­ten and on topic; an an­swer is helpful and an­swers the ques­tion; a com­ment is on topic, thought out, and pro­vides in­sight.

Ex­am­ple: two sen­tence page on The Ma­trix film shouldn’t re­ceive a like, since there isn’t enough con­tent. Definitely do not like the page be­cause you like the movie.

Ex­am­ple: three screen long post ar­gu­ing that global warm­ing is not caused by hu­mans, cit­ing var­i­ous stud­ies and posit­ing an al­ter­na­tive, testable hy­poth­e­sis de­serves a like, even though you prob­a­bly dis­agree with the con­clu­sion. (See the Votes sec­tion be­low.)



There are sev­eral differ­ent types of votes:

  • Prob­a­bil­ity vote is for es­ti­mat­ing the like­li­hood of some propo­si­tion.

  • Ap­proval vote is for mea­sur­ing agree­ment and dis­agree­ment with some propo­si­tion.

For all types of votes, you can see how other peo­ple have voted, and hover over any cluster of votes to see the cor­re­spond­ing user names.

Ex­am­ple: A page ti­tled “Vi­tamin D helps pre­vent can­cer” will have a prob­a­bil­ity bar.

Ex­am­ple: A page ti­tled “Coun­tries with un­sta­ble cur­ren­cies should switch to Bit­coin” will have an ap­proval bar. <div>


You can sub­scribe to pages to re­ceive up­dates when in­ter­est­ing events hap­pen: page is ed­ited, a new com­ment is posted, a child is added, etc… You can also sub­scribe to users to get up­dates when they cre­ate a page or post a com­ment.


A group is a col­lec­tion of users. You can see which groups you be­long to on your Groups page. Be­ing a mem­ber of the group will al­low you to see the group’s pri­vate pages (see “Pri­vate do­main” sec­tion be­low) and edit most pages that the group owns. You might have ad­di­tional ad­min abil­ities like adding/​re­mov­ing group mem­bers.


Pri­vate domain

Each group has a cor­re­spond­ing pri­vate sub­do­main at group­­ All the pages in that sub­do­main are pri­vate to the group, and can’t be seen by any­one else. When you cre­ate a page in that sub­do­main, it will be pri­vate by de­fault. Any page on the de­fault ar­ are pub­lic and can be seen by any­one. <div>


  • Arbital groups

    What are groups? How can I cre­ate a new group?

  • Arbital domain

    What is a do­main? Why is it im­por­tant?

  • Arbital page

    The Ar­bital is a se­ries of pages.

  • Arbital "tag" relationship

    Tags are a way to con­nect pages that share a com­mon topic.

  • Arbital lens

    A lens is a page that pre­sents an­other page’s con­tent from a differ­ent an­gle.

  • Arbital greenlink

    What hap­pens when you hover over an Ar­bital link?

  • Arbital comment

    A com­ment is a way for you to ex­press your thoughts and opinions within the con­text of a page.

  • Arbital page summaries

    Be­cause only one sum­mary is not enough!

  • Arbital requisites

    To un­der­stand a thing you of­ten need to un­der­stand some other things.

  • Arbital path

    Ar­bital path is a lin­ear se­quence of pages tai­lored speci­fi­cally to teach a given con­cept to a user.

  • Arbital mark

    What is a mark on Ar­bital? When is it cre­ated? Why is it im­por­tant?

  • Arbital query

    What is a query? How to cre­ate it? How to re­solve it?

  • Arbital editor

    How to use Ar­bital’s page ed­i­tor.

  • Arbital "requires" relationship

    A page can re­quire a req­ui­site if the reader needs to have it be­fore they are able to un­der­stand the page.

  • Arbital "teaches" relationship

    A page can teach a req­ui­site when the user can ac­quire it by read­ing the page.

  • Arbital "parent" relationship

    Par­ent-child re­la­tion­ship be­tween pages im­plies a strong, in­sep­a­rable con­nec­tion.

  • Arbital likes

    What are likes? When should I use them? What hap­pens when I like some­thing?

  • Arbital subscriptions

    What’s a sub­scrip­tion? How do you change it? What to ex­pect?

  • Arbital Markdown

    All about Ar­bital’s ex­tended Mark­down syn­tax.

  • Arbital content request

    Ar­bital doesn’t ex­plain some­thing you’d like to learn? We’d like to know, so we can pri­ori­tize.


  • Contributing to Arbital

    Want to help Ar­bital be­come awe­some?

    • Arbital

      Ar­bital is the place for crowd­sourced, in­tu­itive math ex­pla­na­tions.