Se manca il lievito, devo impastare di nuovo e aspettare che il pane lieviti.

Mancare means to be missing / to be lacking. So Se manca il lievito literally means If the yeast is missing.

Italian could also use non c’è in some contexts, but manca focuses more clearly on the idea that something needed is absent.

• Manca il lievito = The yeast is missing / We don’t have the yeast
• Non c’è il lievito = There isn’t any yeast / The yeast isn’t there

Both can work, but manca is very natural when talking about an ingredient you need.

Italian often uses the definite article where English would not.

Here il lievito does not necessarily mean one specific yeast in a very narrow sense; it can mean the yeast needed for the recipe or simply yeast in the situation being discussed.

So:

• manca il lievito = the yeast is missing / we’re missing yeast

This is very normal in Italian. English often drops the article with ingredients or materials, but Italian usually keeps it.

Lievito is the noun yeast.

In cooking, it can refer to the leavening agent used to make dough rise. Depending on context, it could mean baker’s yeast, fresh yeast, dry yeast, or even another raising agent, but in a sentence about bread, learners will normally understand it as yeast.

Devo = I must / I have to
impastare = to knead / to mix into dough

So devo impastare means I have to knead or I have to make the dough again, depending on context.

A literal breakdown is:

• devo = I must
• impastare = to knead / to work the dough

In English, the most natural translation may vary:

• I have to knead it again
• I have to make the dough again

Because Italian usually drops subject pronouns when they are clear from the verb form.

• devo already means I must / I have to
• so io devo is possible, but usually unnecessary

You would add io only for emphasis or contrast:

• Io devo impastare di nuovo, non tu.
  I have to knead again, not you.

In a neutral sentence, devo by itself is enough.

Di nuovo means again / anew.

So:

• impastare di nuovo = to knead again

Yes, ancora can sometimes also mean again, but di nuovo is often clearer when talking about repeating an action.

Compare:

• Devo impastare di nuovo. = I have to knead again.
• Devo ancora impastare. = more likely I still have to knead.

So in this sentence, di nuovo is the best choice for again one more time.

Because after aspettare che in Italian, you normally introduce a full clause with its own verb.

• aspettare che il pane lieviti = to wait for the bread to rise

You cannot say aspettare il pane lievita because that would combine a direct object (il pane) with a finite verb (lievita) in an ungrammatical way.

The correct patterns are:

• aspettare qualcosa = to wait for something
• aspettare che + verb = to wait until / to wait for ... to ...

Here the speaker is waiting for an action to happen, so Italian uses che + verb.

Because after aspettare che, Italian normally uses the subjunctive.

The verb is lievitare = to rise / to leaven.

Present indicative:

• il pane lievita = the bread rises

Present subjunctive:

• che il pane lieviti

So in this sentence:

• aspettare che il pane lieviti

uses the subjunctive because the rising of the bread is something expected or awaited, not simply stated as a fact.

Context tells you.

Here che il pane lieviti follows aspettare che, so lieviti must be a verb form. It is the present subjunctive of lievitare.

Also:

• il pane is singular
• so the verb must match a singular subject

If lieviti were a noun, it would mean yeasts, but that would not fit the structure of the sentence.

So here:

• lievito = noun, yeast
• lieviti = verb, (that) it rise

This is a nice example of related words:

• lievito = yeast
• lievitare = to rise / to leaven

This is a normal, real-condition sentence.

• Se manca il lievito = If the yeast is missing
• devo impastare di nuovo = I have to knead again

Italian often uses:

• se + present indicative
• present, future, or another suitable tense in the main clause

Here both parts are in the present because the speaker is expressing a general or immediate consequence:

• If the yeast is missing, I have to knead again and wait...

This is not a hypothetical contrary-to-fact sentence like If I had... I would...

It can cover both ideas depending on context.

Impastare is related to making a dough or paste. In baking contexts, it may mean:

• to mix the ingredients into a dough
• to knead the dough

So the best English translation depends on the situation. In your sentence, if the dough has to be redone because the yeast is missing, make the dough again or knead again may both be acceptable.

The comma separates the conditional clause from the main clause:

• Se manca il lievito,
• devo impastare di nuovo...

This is very common and helps readability. In Italian, commas after an initial se clause are often used just as in English:

• If the yeast is missing, I have to...

You may sometimes see variation in informal writing, but the comma is perfectly standard here.

No. Lievitare means to rise / to increase in volume because of yeast or another leavening agent.

It is very common with doughs and baked goods:

• Il pane lievita. = The bread rises.
• La pizza deve lievitare. = The pizza dough has to rise.

So it is strongly associated with baking, not just with bread.

Yes, in some contexts reimpastare can be used and means to knead/remake the dough again. But impastare di nuovo is very transparent and easy to understand.

• reimpastare = to knead again / remake the dough
• impastare di nuovo = literally to knead again

The version in your sentence is straightforward and very natural for learners to recognize.