Terms of use

Dhana — version of 11 October 2026

These terms say what Dhana offers you, what you can expect from it, and what we expect from you. They apply as soon as you sign in to the app. What Dhana does with your data is described separately, in the privacy policy.

Who offers Dhana

René Obe, publisher of Dhana.
Postal address: Schloßstraße 2, 53115 Bonn, Germany
Email: rene@perihelie-labs.net

Email is the way to reach us, for any question and to report content; we usually reply within a few days, in French, German or English.

What Dhana is

An Android app for learning a language. You type the name of a situation or of the place where it happens (at the doctor's, at the station), of an activity (cooking, playing chess) or of a work (a film, a series, a book, a game). Dhana writes a card in the language you are learning, explained in your own, and you review it one flashcard at a time. You can also ask a question about a word or a sentence, have your own sentences translated, and keep your personal cards.

Lastly, you can paste a text you are reading elsewhere — an article, a page from a book, song lyrics. Dhana turns it into a card for you alone: each paragraph with its translation, and the words from the text for you to review.

Not everything makes a card. Faced with a name it does not know yet, Dhana first checks that there is enough to write one — a situation where you talk to someone, or an activity with its own vocabulary — and tells you if there is not.

You need a Google account to sign in, and an internet connection to have a card written, ask a question or translate. What you already have can be read and reviewed without a connection.

Cards are written by language models

Every card is written by a language model, then checked automatically: first its form, then its content, which two models read through — in every language except Egyptian Arabic, where this second reading is not yet reliable. What they object to is corrected, or the card is written again. No person reads a card before it reaches you. This check removes most mistakes; it does not remove all of them.

So a card can contain an error: an approximate translation, a wrong gender or construction, a sentence less natural than it should be, a detail of a work misreported. The same goes for the answers to your questions and the translations of your sentences.

Dhana is made for learning a language, not to serve as an authority. Before you send a text that commits you — an official letter, a contract, medical information — have it read by someone who speaks the language.

When you find a mistake, the link “Report an error on this card”, at the bottom of the card, sends it to us. We read every report and correct the card when it is wrong; the corrected card is then offered on every phone that has it. A report does not carry your name, so we cannot reply to you.

A card made from a text you pasted does not have this link: it exists only on your phone, and you correct it yourself, from the menu of a word or a paragraph.

Your account

• Dhana is intended for people aged thirteen and over. Under eighteen, you need the agreement of a parent or guardian to use it, and it is the parent or guardian who decides on a subscription.
• An account belongs to one person only: do not lend it, do not share it.
• You can delete your account at any time, in the app's Settings; if you no longer have the app, the page dhana.eu/delete-account says how. Deleting the account does not cancel a current subscription: cancel it first in Google Play, otherwise it goes on being charged.
• An account with no current subscription, which nobody has signed in to for twenty-four months, is deleted, along with its backup if there is one.

What you learn lives on your phone

Your shelf — the cards you have taken —, your flashcards and their review schedule, your collections, your personal cards, the cards made from your texts, your sentences and your notes are stored on your phone, not with us. Uninstalling the app, clearing its data or losing the phone erases them, and we cannot give them back to you: we have no copy.

Two actions in Settings give you one: “Back up to the server” stores a copy attached to your account, and “Export to a file” produces a file that you keep wherever you like. The server keeps only one backup per account, the latest: each new backup replaces the previous one. Do one or the other before you change phones.

Plans and their limits

Dhana counts four things: the cards you take, the questions you ask, the sentences you have translated, and suggestions — a name Dhana does not know yet, for which you ask it to write a card.

• The free trial has no time limit and asks for no means of payment: its numbers apply once and for all, and nothing is charged when they run out. The cards you have taken stay yours.
• The month runs from date to date, starting on the day the subscription began. This is also true of the annual subscription: a paid year gives a hundred cards each month, not a hundred for the year. What is not used in a month does not carry over.
• One counter for all languages: a card in German and a card in Russian make two cards.
• What counts. A card counts when it arrives on your shelf, whether it has just been written for you or already existed. A card whose writing failed does not count; a card removed and taken back does not count a second time; a personal card, which you write yourself, does not count. A text you paste counts as a card when its card arrives; the same text, pasted again, does not count a second time. A question counts as soon as it is asked, even if Dhana cannot answer it; a translation, on every request; a suggestion, as soon as Dhana examines it, whether it accepts it or not. “My limits”, in Settings, shows what is left and the date of the next month.
• Per hour, a subscription gives at most twenty questions, sixty translations and twenty suggestions; a limit that has been reached lifts within the hour. The free trial is too small to reach them. For everyone: thirty reports an hour, and a few other limits, far higher, which are only there to stop an automated program.
• The top-up, reserved for subscribers, adds half a month: 50 cards, 150 questions, 500 translations, 50 suggestions. It is a reserve with no expiry date: it is drawn on only once the month is used up, and the renewal of the subscription does not touch it. If the subscription ends, what is left of it can still be used, until it runs out.

Payment, renewal, cancellation

• The subscription — monthly or annual — and the top-up are bought in the app, through Google Play. The price is the one shown by the app and by Google Play at the time of purchase, all taxes included. Google Play collects the payment on our behalf; the contract is made with us. We never see your means of payment.
• The subscription renews by itself at the end of each period, at the same price, as long as you have not cancelled it.
• You can cancel it at any time, in Google Play (Payments and subscriptions). Cancelling stops the renewal; the subscription runs to the end of the period already paid for, which is not refunded — except in the two cases that follow.
• Within fourteen days of the purchase, you can withdraw without giving a reason — by writing to us, or by asking for the refund in Google Play —, and we refund the full price, even if you have already started using what you bought. The legal information and the form are below.
• The annual subscription, after its first year. Once renewed, it can be cancelled at any time: write to us, and we refund, pro rata, the whole months that have not begun.
• If the price of a subscription changes, Google Play tells you before it applies, and you can cancel beforehand. A change never affects a period already paid for.

When the subscription ends

Everything you have stays: the cards on your shelf, their flashcards and their review schedule, your collections, your personal cards, your sentences and your notes. You go on reading them, reviewing them and practising. What stops is anything new: no new card, question or translation, until a new subscription — except what is left of a top-up.

What you ask for, and what others will see

A card written at your request joins a shared catalogue: another person who asks for the same work or the same situation will receive the same card, without ever knowing who asked for it first. The name of a situation or an activity you suggest, once accepted, also appears in other people's searches. So what you ask for has readers, and the rules that follow exist for them.

A card made from a text you paste is an exception: it is written for you alone, does not join the catalogue, and nobody else receives it — not even someone who pastes the same text.

Works, including the darkest. You can ask for a card on any work Dhana finds — film, series, book, play, game —, including when its subject is war, crime, dictatorship or propaganda. A piece of propaganda is also a historical document, and to read it, study it or talk about it in another language, you need its vocabulary. A card teaches the words for talking about a work; it does not adopt the work's point of view. It describes, in everyday language, with nothing sexually explicit.

What we remove or refuse to write:

• a card which, instead of describing, would glorify hatred, violence or discrimination;
• a suggestion whose name insults, targets a real person, calls for hatred or violence, or is sexually explicit;
• anything that would serve as instructions for causing harm — making a weapon or a drug, for example;
• any content that is illegal under German law or the law of the European Union.

The language models Dhana uses also have their own rules: they sometimes refuse a subject, or speak of it less precisely than one would expect. A refused card does not count.

If a card or a name seems to you to cross these lines, report it through the link at the bottom of the card, or write to us; anyone can report illegal content to us at the address at the top of this page, even without an account. We examine every report and remove what has to be removed.

The texts you paste

The text you paste comes from you, and you are responsible for it: paste texts you have lawful access to, and nothing illegal — an article, a page from a book, song lyrics —, to study them yourself. Dhana fetches no text on its own.

The text goes to the language model to write your card, then the server forgets it: it does not keep it, shows it to no one and uses it for nothing else. Dhana does not judge what you paste and does not correct its mistakes: a text you wrote yourself, or one not written by a native speaker, can bring its mistakes into your reviews.

What we expect from you

Use Dhana for what it is: learning. In particular, do not use the app's fields to insult or harass, do not try to divert the language models from their task, do not get round the limits of the plans, do not query the service with an automated program, do not copy the catalogue in bulk, and do not resell access to your account.

In case of abuse, we may refuse a request, or suspend or close an account, in proportion to what happened. We then write to you, at the address of your Google account, to tell you what we did and why; you can reply to contest it.

What is yours, what is ours

• Your sentences, your notes, your personal cards are yours. They stay on your phone, except in the backup you make yourself. When you send a sentence to have it translated or to ask a question, we use it only to answer you.
• The catalogue's cards are free to use. You can print them, save them as PDF, hand them out to a class, share them, adapt them — without asking us. A mention of Dhana is appreciated; it is not required. The cards made from your texts are not: they reproduce a text that belongs to its author, and are for your personal use.
• The app and the catalogue, taken as a whole, are ours. Extracting a substantial part of it — to feed another app, another service or a language model — requires our agreement.
• The works belong to their authors. A card talks about a work; it is not meant to reproduce its text. Dhana is not affiliated with any author, studio or publisher, and their titles and names belong to them.

Availability

We work to keep Dhana running, but an online service has outages and maintenance, and depends on providers — the language model first of all. During an interruption, your cards remain readable and reviewable on the phone. The app evolves: a feature may change form, without reducing what your subscription gives you during a period you have paid for.

If Dhana were to stop for good, we would announce it in the app at least thirty days in advance, and the part of the subscription paid for and not provided would be refunded. What is on your phone would stay there, and the export lets you keep a copy of it.

Liability

We are liable without limit for damage caused intentionally or by gross negligence, for injury to life, body or health, and in the cases where the Product Liability Act requires it. For slight negligence, we are liable only for the breach of an essential obligation — an obligation without which the contract cannot be performed and on which you must be able to rely —, and only for the foreseeable damage typical of this kind of contract. Beyond that, our liability is excluded.

An error in a card, as described in the section on language models, is not in itself a breach: it is a known limit of the service, stated in advance.

If these terms change

Every version carries its date at the top. A change is announced in the app at least thirty days before it applies. If it affects what you pay or what your plan gives you, we ask for your agreement; without it, you can cancel, and the current period remains governed by the terms under which you paid for it.

Your right of withdrawal

If you are a consumer, what follows applies to the subscription and to the top-up alike. It is the model information the law provides, taken as it is; what we add to it — the full refund, even after use, and the option of asking in Google Play — is said above, in “Payment, renewal, cancellation”.

Withdrawal information

Right of withdrawal. You have the right to withdraw from this contract within fourteen days without giving any reason. The withdrawal period will expire after fourteen days from the day of the conclusion of the contract.

To exercise the right of withdrawal, you must inform us (René Obe, Schloßstraße 2, 53115 Bonn, Germany, rene@perihelie-labs.net) of your decision to withdraw from this contract by an unequivocal statement (e.g. a letter sent by post or e-mail). You may use the model withdrawal form below, but it is not obligatory. To meet the withdrawal deadline, it is sufficient for you to send your communication concerning your exercise of the right of withdrawal before the withdrawal period has expired.

Effects of withdrawal. If you withdraw from this contract, we shall reimburse to you all payments received from you, without undue delay and in any event not later than fourteen days from the day on which we are informed about your decision to withdraw from this contract. We will carry out such reimbursement using the same means of payment as you used for the initial transaction, unless you have expressly agreed otherwise; in any event, you will not incur any fees as a result of such reimbursement.

Model withdrawal form
(Complete and return this form only if you wish to withdraw from the contract.)

— To René Obe, Schloßstraße 2, 53115 Bonn, Germany, rene@perihelie-labs.net:
— I/We (*) hereby give notice that I/We (*) withdraw from my/our (*) contract of sale of the following goods (*)/for the provision of the following service (*),
— Ordered on (*)/received on (*),
— Name of consumer(s),
— Address of consumer(s),
— Signature of consumer(s) (only if this form is notified on paper),
— Date
(*) Delete as appropriate.

Governing law and disputes

These terms are governed by German law. If you are a consumer, you keep the protection given to you by the mandatory rules of the country where you live, and you can bring a case before the courts of that country.

In case of disagreement, write to us first: most problems are settled by an email. We do not take part in dispute resolution proceedings before a consumer arbitration board, and are not obliged to.