Terms of use.
These are the terms for Lemma, the app, and for lemma.day. They sit on top of Apple's standard licence for apps, which applies to every app from the App Store: Apple's standard licence agreement. Last updated 13 October 2026.
Who we are
Lemma is published by Eudaimonia Tech Srl, company number J40/8792/2023, VAT code RO48149202, registered at Str. Opanez nr. 7, bl. 73, sc. 2, ap. 39, Bucharest, Romania. Contact: [email protected].
The free lemma
One lemma a day is free forever, with no ads, and includes your notebook, sequence, circles and the global board.
Lemma Plus
Lemma Plus adds unlimited corollaries at four difficulties, the archive of past daily lemmas and the rewards from your theorems. It is a subscription sold through the App Store.
| Plan | Price | Free trial |
|---|---|---|
| Yearly | $19.99 a year | 7 days |
| Monthly | $2.99 a month | None |
| Family | $29.99 a year, up to 6 people with Family Sharing | 7 days |
- Prices are in US dollars; the App Store shows the price in your own currency.
- Payment is charged to your Apple account when you confirm the purchase, or when a free trial ends if you do not cancel first.
- The subscription renews automatically for the same period at the same price, unless you cancel at least 24 hours before the current period ends.
- Manage or cancel it at any time in your Apple account settings. Cancelling stops the next renewal; you keep Lemma Plus until the end of the period you paid for.
- Refunds are handled by Apple under its own rules.
- On the family plan, the person who buys it shares it with their Family Sharing group, up to 6 people.
Fair play
Boards are for honest times. A solve that fails our validation, for example one that could not have been played by hand, may be left off the boards. Your own notebook is not affected.
Your account
You can use Lemma without signing in. If you sign in with Apple, you are responsible for what happens under your account. You can delete it at any time in the app, as described in the privacy policy.
Using Lemma
Do not misuse the service: no automated play, no attempts to break the boards, and no names in circles that harass others. We may remove a circle member or a display name that does.
Liability
Lemma is provided as it is, and we work to keep it running. To the extent the law allows, we are not liable for indirect loss. Nothing here limits your rights as a consumer under the law of your country.
Governing law
These terms are governed by Romanian law, without affecting the mandatory consumer rights you have where you live.
Changes
If we change these terms in a way that matters, we update the date above and tell you in the app.