Adiós; hasta mañana.

One is enough.

Spanish often combines farewells, so Adiós; hasta mañana feels natural as a fuller goodbye, like Bye, see you tomorrow. But you can also say just:

Adiós
or
Hasta mañana

Using both simply sounds a bit warmer or more complete.

It is definitely used, but in Spain it can sometimes sound a little more definite or more serious than some other everyday goodbyes.

Among friends, people often say things like hasta luego, nos vemos, or chao. Adiós is still perfectly normal, but depending on tone and context, it can feel slightly more final than bye in English.

So in Adiós; hasta mañana, the second part softens that feeling and makes it clear that you expect to see the person again soon.

Because hasta mañana is a fixed farewell expression.

Spanish often leaves out words that are understood from context. Literally, hasta means until, and mañana means tomorrow, so the phrase is basically until tomorrow. In natural English, that usually corresponds to see you tomorrow rather than a word-for-word translation.

So even though there is no verb written, the idea is complete and idiomatic.

The semicolon links two closely related parts: Adiós and hasta mañana.

Because a semicolon does not begin a new sentence, the next word stays lowercase: hasta, not Hasta.

That said, in everyday writing, many people would more often write:

Adiós, hasta mañana.
or
Adiós. Hasta mañana.

So the semicolon is understandable, but a comma or full stop is more common in casual writing.

Because Spanish accent marks follow pronunciation rules.

Adiós has the stress on the last syllable: a-di-ÓS. Words ending in a vowel, n, or s are normally stressed on the second-to-last syllable, so the written accent is needed to show that adiós is an exception.

Mañana is stressed on the second-to-last syllable: ma-ÑA-na. Since that stress pattern is exactly what Spanish spelling rules predict for a word ending in a vowel, no accent mark is needed.

So: adiós = accent mark needed
mañana = no accent mark needed

A helpful approximation is:

adiós → ah-DYOS
hasta mañana → AHS-ta ma-NYA-na

A few useful details:

In adiós, the dio sounds like one syllable: dyos, not dee-ohs.

The ñ in mañana sounds like the ny in canyon.

In much of Spain, the d in adiós is softer than a strong English d, especially between vowels.

The h in hasta is silent.

If you want a rough Spain-style pronunciation of the whole phrase, it is close to:

ah-DYOS; AHS-ta ma-NYA-na

Use hasta mañana when tomorrow is genuinely the expected next time you will see or speak to the person.

For example, it works well with classmates, coworkers, or anyone you know you will meet again the next day.

If tomorrow is uncertain, Spanish speakers usually prefer something less specific, such as hasta luego or nos vemos.

So it is not just a general goodbye; it normally refers to an expected tomorrow.

Yes. In Spain, some very common alternatives are:

Hasta luego — a very common general goodbye
Nos vemos — see you
Hasta mañana — when you expect to see them tomorrow
Chao — casual bye

Compared with these, adiós is still correct and common, but it can feel a little more marked depending on tone and situation.

So if you want a very everyday Spain-style farewell, you will often hear things like:

Hasta mañana
Hasta luego
Nos vemos mañana