Last updated: 26 July 2026
These terms govern your use of Erudia (the "Service") at erudia.org. By creating an account or using the Service, you agree to them.
You must be at least 13 years old to use Erudia. You must provide an accurate email to create an account and are responsible for activity under it; keep your password secure. If you are under 18, please use Erudia with a parent or guardian's awareness.
Erudia provides interactive mathematics lessons and a spaced-repetition review system. We may add, change, or remove features as the product evolves.
Use Erudia to learn. Don't do any of the following:
We may remove content, suspend an account, or end access when we believe this section has been broken. We're not obliged to warn you first, and we're not liable for having done so.
Erudia offers an optional Premium subscription at $7.99 per month. Key terms, which are also shown before you pay:
If you create content in the community (for example, practice problems), you keep ownership of it. You grant Erudia a worldwide, non-exclusive, royalty-free, perpetual, irrevocable, sublicensable and transferable licence to host, store, reproduce, modify, adapt, translate, publish, publicly display and distribute that content in connection with operating, improving and promoting the Service.
That licence continues after you delete your account to the extent your content has been built into shared material, such as a community problem set other learners are working through — one deletion shouldn't break someone else's practice queue. We'll detach your name from it on request.
You're responsible for what you submit. You must have the right to share it, and you must not submit material copied from a copyrighted source, including competition problems you don't have permission to reproduce.
We don't have to publish, host, or keep hosting anything. We may decline, edit, or remove community content at our discretion, and we're under no obligation to store or return it.
The Erudia name, lessons, curriculum, software, and design are owned by us and protected by law. We grant you a personal, non-transferable right to use the Service for learning.
We respect intellectual-property rights and expect the same of our community. If you believe content on Erudia (including a community-submitted problem) infringes your copyright, email erudia@erudia.org with: (a) identification of the copyrighted work, (b) the URL or location of the material on Erudia, (c) your contact information, (d) a statement that you have a good-faith belief the use is not authorized, and (e) a statement, under penalty of perjury, that the information is accurate and you are the owner or authorized to act for the owner. We will review notices promptly, remove infringing material where appropriate, and may terminate the accounts of repeat infringers.
Counter-notification. If your content was removed and you believe that was a mistake or a misidentification, email us a counter-notice with: (a) identification of the removed material and where it appeared, (b) a statement under penalty of perjury that you have a good-faith belief it was removed by mistake or misidentification, (c) your name, address, and phone number, and (d) your consent to the jurisdiction of the federal court for your district (or, if you're outside the United States, for the Northern District of Illinois). We may restore the material after a waiting period unless the original complainant files a court action.
Repeat infringers. We keep a record of copyright complaints and terminate, in appropriate circumstances, the accounts of users who repeatedly infringe.
Erudia is an educational tool provided "as is" and "as available." To the fullest extent permitted by law, we disclaim all warranties, express or implied, including any implied warranties of merchantability, fitness for a particular purpose, title, and non-infringement. We don't guarantee specific learning outcomes, uninterrupted or error-free operation, or that the Service will meet your requirements.
Content accuracy. Lessons, worked solutions, and generated practice questions may contain errors. Erudia is a study aid, not an authority — check anything you're relying on for an exam, a grade, or a submission.
Not professional advice. Some chapters cover financial, actuarial, and statistical mathematics, and the Service includes market and probability simulations. Those are teaching tools. Nothing in the Service is financial, investment, tax, legal, or other professional advice, and no simulation predicts real-world results.
Your progress data. We sync and back up your progress on a best-effort basis. We don't guarantee it against loss or corruption, and we aren't liable if it's lost. You can export everything as a JSON file from Settings at any time, and you should, if it matters to you.
Experiments and moving parts. We run A/B experiments on parts of the learning engine (see the Privacy Policy) and sometimes ship features that are new or incomplete. Features can change, move, or be withdrawn.
To the fullest extent permitted by law, Erudia and anyone operating it will not be liable for indirect, incidental, special, consequential, exemplary, or punitive damages, or for lost profits, lost data, lost goodwill, or the cost of substitute services — however caused, under any theory of liability, and even if we were advised such damages were possible.
Our total aggregate liability for all claims relating to the Service is limited to the greater of (a) what you paid us in the 12 months before the event giving rise to the claim, or (b) US$100.
These limits apply even if a limited remedy fails of its essential purpose. Some places don't allow certain exclusions, so parts of this section may not apply to you; where that's the case, our liability is limited to the smallest amount the law allows.
You agree to indemnify and hold harmless Erudia and anyone operating it from any claim, demand, loss, liability, or expense (including reasonable legal fees) arising out of (a) content you submit, (b) your use of the Service, (c) your breach of these terms, or (d) your violation of anyone else's rights. We may take over the defence of any such claim at your expense, and you won't settle it in a way that puts any obligation on us without our written consent.
Any claim arising out of or relating to these terms or the Service must be brought within one year after it arises, or it is permanently barred — except where applicable law doesn't allow a shortened period.
These terms are governed by the laws of the State of Illinois, United States, without regard to conflict-of-law rules. You and Erudia agree to the exclusive jurisdiction of the state and federal courts located in Cook County, Illinois, except where your local consumer-protection law gives you the right to bring proceedings where you live.
Individual claims only. You and Erudia agree to bring claims against each other only in an individual capacity, and never as a plaintiff or class member in any class, collective, consolidated, or representative proceeding. A court may not consolidate more than one person's claims or preside over any representative action. If this paragraph is held unenforceable, the rest of this section still applies.
Jury trial. To the extent the law allows, you and Erudia each waive any right to a jury trial in a proceeding arising out of these terms or the Service.
What this doesn't take away. You keep the right to bring an individual claim in small-claims court, and nothing here stops either of us from asking a court to stop an ongoing infringement of intellectual property. We have deliberately not put a forced-arbitration clause in these terms: it would take away your right to go to court, and we'd rather you keep it.
You can stop using Erudia and permanently delete your account anytime from Settings → Delete account. We may suspend or terminate accounts that violate these terms; where we terminate for a violation, unused subscription time isn't refunded. If we discontinue the Service entirely, we'll give reasonable notice and refund the unused part of any prepaid period.
We may update these terms. Material changes will be notified in the app and, if you're a subscriber, take effect at your next renewal. Continued use after that means acceptance.
Questions: erudia@erudia.org · Privacy Policy · Accessibility