Одноразовий пароль потрібний для мобільного банкінгу.

In Ukrainian, the present-tense verb to be is usually omitted in sentences like this.

So:

Одноразовий пароль потрібний для мобільного банкінгу.

literally looks like:

One-time password needed for mobile banking.

But it naturally means A one-time password is needed for mobile banking.

This is very normal in Ukrainian. English requires is, but Ukrainian usually does not.

Одноразовий пароль is in the nominative singular.

That is because it is the thing being described as needed. In other words, it is the grammatical subject of the sentence.

The adjective одноразовий agrees with пароль in:

• gender: masculine
• number: singular
• case: nominative

So the form is:

• одноразовий = masculine nominative singular
• пароль = masculine nominative singular

Yes, you can also say потрібен.

Both are possible, but they are slightly different in style:

• потрібний = the full adjective form
• потрібен = a short predicative form, very common in everyday Ukrainian

So these are both natural:

• Одноразовий пароль потрібний для мобільного банкінгу.
• Одноразовий пароль потрібен для мобільного банкінгу.

In modern usage, потрібен often sounds a bit more conversational and common in this kind of sentence, while потрібний can sound a little more formal or bookish.

Because the preposition для requires the genitive case.

The basic dictionary form is:

• мобільний банкінг

After для, both words change to genitive singular:

• мобільного банкінгу

So:

• мобільний → мобільного
• банкінг → банкінгу

This is a very important pattern in Ukrainian: the preposition often determines the case of the following noun phrase.

Because банкінг is a masculine noun, and in the genitive singular many masculine nouns take -у or -ю, especially abstract nouns, processes, fields, or borrowed terms like this one.

So:

• банкінг → банкінгу

This is similar to other modern loanwords and abstract nouns. It is not always fully predictable from English, so it is often best to learn the genitive form together with the noun.

In this sentence, банкінга would not be the normal form.

Одноразовий literally means for one use or single-use.

So одноразовий пароль means a password that is meant to be used only once.

It comes from the idea of один раз = one time / once.

You will also see одноразовий with other nouns, for example:

• одноразовий код = one-time code
• одноразовий посуд = disposable tableware

So in this sentence, it specifically means one-time, not just temporary in a vague sense.

It is a borrowing from English, but it is also a normal and widely used word in modern Ukrainian, especially in finance and technology.

Expressions like these are very common:

• інтернет-банкінг
• мобільний банкінг

So мобільний банкінг sounds natural and standard, especially in banking, apps, websites, and official instructions.

Yes. Ukrainian word order is more flexible than English word order.

For example, this is also natural:

Для мобільного банкінгу потрібний одноразовий пароль.

The meaning stays basically the same, but the emphasis changes a little.

• Одноразовий пароль потрібний для мобільного банкінгу.
  Focuses first on the one-time password.

• Для мобільного банкінгу потрібний одноразовий пароль.
  Focuses first on mobile banking as the context.

So word order in Ukrainian often helps show emphasis, topic, or what the speaker wants to highlight first.

Not if you want exactly the same meaning.

• для мобільного банкінгу = for mobile banking, meaning it is required in order to use it
• у мобільному банкінгу = in mobile banking, meaning within that sphere or system

So in your sentence, для is the natural choice because the idea is that the password is needed for the purpose of mobile banking.

Yes. Необхідний also means necessary / required.

For example:

Одноразовий пароль необхідний для мобільного банкінгу.

This sounds a bit more formal than потрібний or потрібен.

A rough style comparison is:

• потрібен = very common, everyday
• потрібний = normal, slightly more formal/literary
• необхідний = more formal, official, or technical

So all three can work, but the tone changes a little.