La tutina resta asciutta dopo il bagnetto.

Because tutina is a singular feminine noun, so it normally takes the definite article la when you are talking about the onesie/sleeper in a general or specific context.

• la tutina = the onesie
• una tutina = a onesie

Italian uses articles very frequently, often more than English does.

The ending -ina is a diminutive ending. It often makes a word sound:

• smaller
• cuter
• more affectionate

So tutina comes from tuta and suggests a little suit/onesie, often something for a baby.

This is very common in Italian:

• casa → casina
• gatto → gattino
• bagno → bagnetto

Resta is the third-person singular form of restare.

Here, restare means to stay or to remain, not just to be. The idea is that after the bath, the garment continues to be dry.

So resta asciutta has the sense of:

• stays dry
• remains dry

That is slightly different from simply saying è asciutta, which would just describe its condition, not emphasize that it keeps that condition.

Because adjectives in Italian usually agree with the noun they describe.

Tutina is:

• singular
• feminine

So the adjective must also be:

• singular
• feminine

That gives:

• asciutta = feminine singular

Compare:

• la tutina è asciutta
• il body è asciutto
• le tutine sono asciutte
• i vestiti sono asciutti

It is a time expression meaning after the bath.

• dopo = after
• il bagnetto = the little bath / baby’s bath

So this phrase tells you when the onesie stays dry.

Italian often uses dopo + article + noun:

• dopo il pranzo = after lunch
• dopo la scuola = after school
• dopo il bagnetto = after the bath

Bagnetto is another diminutive. It comes from bagno.

In everyday Italian, especially when talking about babies or small children, bagnetto is very common and sounds affectionate. It often refers specifically to a baby’s bath.

So:

• bagno = bath / bathroom / wash, depending on context
• bagnetto = little bath, often a baby bath

It is not only about size; it can also express tenderness or familiarity.

Because bagnetto is a masculine singular noun, and here it is used with the definite article il.

So:

• il bagnetto = the bath

The preposition dopo is simply followed by the noun phrase:

• dopo il bagnetto

Unlike in some other Italian combinations, there is no contraction here. It is not a fused form like del or nel.

No, this is a very normal Italian word order:

La tutina + resta + asciutta + dopo il bagnetto

That is:

• subject
• verb
• adjective/complement
• time phrase

Italian word order is often flexible, but this version is neutral and natural.

You could move the time phrase for emphasis:

• Dopo il bagnetto, la tutina resta asciutta.

That still sounds natural.

Yes. Rimane asciutta is also correct and natural.

Both restare and rimanere can mean to remain / to stay in this kind of sentence.

Very roughly:

• resta asciutta = stays dry
• rimane asciutta = remains dry

In many everyday contexts, they are interchangeable. Resta may sound a little simpler and more direct.

Yes. It comes from restare, which is a regular -are verb in the present tense.

Present tense:

• io resto
• tu resti
• lui/lei resta
• noi restiamo
• voi restate
• loro restano

In the sentence, the subject is la tutina, which is third-person singular, so resta is the correct form.

Yes, very easily. It sounds natural in contexts like:

• baby clothing
• diapers
• absorbent fabrics
• bath-time products

That is because it is short, clear, and highlights a useful result: the garment stays dry after bath time.

The use of tutina and bagnetto also gives it a warm, baby-related tone.