Я хочу відправити листівку поштою сьогодні.

Yes, you often can. Ukrainian verb endings usually make the subject clear, so Хочу відправити листівку поштою сьогодні is also natural.

Including Я adds emphasis or clarity, especially if you want to stress I rather than someone else.

So:

• Я хочу... = I want...
• Хочу... = Want... / I want...

Both are correct.

After хочу meaning I want, Ukrainian normally uses the infinitive of the second verb.

So the pattern is:

• хочу + infinitive
• хочу відправити = want to send
• хочу купити = want to buy
• хочу піти = want to go

Here:

• хочу = I want
• відправити = to send

This is about aspect, which is very important in Ukrainian verbs.

• відправити is perfective: it focuses on a completed action, a single sending
• відправляти is imperfective: it focuses on process, repetition, or general activity

In this sentence, хочу відправити means the speaker wants to send the postcard as a completed action, so the perfective verb fits naturally.

Compare:

• Я хочу відправити листівку сьогодні = I want to send the postcard today, as one completed act
• Я хочу відправляти листівки щотижня = I want to send postcards every week

Because it is the direct object of the verb відправити, so it goes into the accusative case.

Листівка is a feminine noun. In the singular, many feminine nouns ending in -а change to -у in the accusative:

• листівка → листівку
• книга → книгу
• машина → машину

So листівку means a postcard as the thing being sent.

Because поштою is the instrumental case, used here to mean by mail or through the post.

This is a common Ukrainian pattern:

• їхати автобусом = to go by bus
• писати олівцем = to write with a pencil
• відправити поштою = to send by mail

So:

• пошта = post/mail, dictionary form
• поштою = by mail

No. Поштою means by mail or through the postal service.

If you want to say at the post office, you would use something like:

• на пошті = at the post office

So these are different:

• відправити листівку поштою = send a postcard by mail
• бути на пошті = be at the post office

Ukrainian word order is fairly flexible. Сьогодні can often move around without changing the basic meaning.

For example:

• Я хочу відправити листівку поштою сьогодні
• Я сьогодні хочу відправити листівку поштою
• Сьогодні я хочу відправити листівку поштою

All of these can work.

The difference is mostly emphasis:

• Сьогодні я хочу... puts extra focus on today
• Я хочу... сьогодні sounds like today is added at the end as the time detail

Usually yes, especially in a sentence like this. Листівка most commonly means postcard.

In some contexts it can also refer to a card, depending on usage, but if you are talking about sending something поштою, postcard is the most natural understanding.

Yes. Надіслати is also a very common verb meaning to send.

Both are correct, but there can be slight differences in feel depending on context:

• відправити often feels like send off / dispatch
• надіслати often feels like send in a general sense

For a postcard, either can work:

• Я хочу відправити листівку поштою сьогодні
• Я хочу надіслати листівку поштою сьогодні

Both are natural.

Ukrainian has no articles like English a/an/the.

So листівку can mean:

• a postcard
• the postcard

The exact meaning depends on context.

This is very normal in Ukrainian, so learners need to get used to understanding definiteness from the situation rather than from an article.

Ukrainian relies a lot on case endings and verb forms, not just word order.

In this sentence:

• Я is the subject
• хочу shows first person singular: I want
• відправити is the infinitive: to send
• листівку has accusative ending, so it is the object
• поштою has instrumental ending, so it shows means: by mail
• сьогодні is the time expression: today

Because of those forms, Ukrainian can move words around more freely than English.

A learner-friendly pronunciation is roughly:

• vid-PRÁ-vy-ty

The stress is on пра: відпра́вити.

A few useful stress points in the whole sentence:

• хочу́
• відпра́вити
• листі́вку
• пошто́ю
• сього́дні

Stress matters in Ukrainian, so it is good to learn words together with their stressed syllables.

Yes, it is natural and correct.

A native speaker might also say similar versions such as:

• Я хочу сьогодні відправити листівку поштою
• Сьогодні хочу відправити листівку поштою
• Я хочу надіслати листівку сьогодні

But your sentence is perfectly normal and understandable.