Learn Hardcore Spanish (Latin America): Hoy desayuno avena con plátano; es simple y saludable. - Today I have oatmeal with banana for breakfast; it is simple and healthy.

So Hoy desayuno avena… literally means “Today I-have-breakfast oats…”.
You don’t need to add como (I eat), because desayunar already includes the idea of eating breakfast.

Could I say Yo desayuno avena con plátano? Why is yo left out?

Yes, Yo desayuno avena con plátano is correct.

Spanish usually drops subject pronouns (yo, tú, él, etc.) because the verb ending already shows who is doing the action.

Desayuno can only mean yo desayuno in the present tense.
Adding yo often adds emphasis:
- Yo desayuno avena… = I (as opposed to someone else) eat oatmeal…

Is desayuno a noun too? How do I know if it means “breakfast” or “I have breakfast”?

Yes, desayuno is both:

Verb: (yo) desayuno = I have breakfast.
Noun: el desayuno = the breakfast.

You know which it is from the structure of the sentence:

Hoy desayuno avena… → After hoy, you expect a verb, so desayuno = I have breakfast.
Mi desayuno es avena con plátano. → After mi, you expect a noun, so desayuno = breakfast.

Why is it Hoy desayuno and not Desayuno hoy? Are both correct?

Both are grammatically correct.

Hoy desayuno avena…
Slight emphasis on “today”; it feels natural and common.
Desayuno hoy avena…
Also possible, but less common and can sound a bit more marked.

In everyday speech, putting hoy first is very typical: Hoy trabajo, Hoy no salgo, Hoy desayuno avena.

Why is there no article before avena or plátano (why not la avena or un plátano)?

In Spanish, when talking about what you usually eat/drink (especially for meals), you often omit the article:

Desayuno avena. = I eat oatmeal (for breakfast).
Tomo café. = I drink coffee.
Como arroz. = I eat rice.

You would use an article when you’re being more specific:

Desayuno la avena que sobró de ayer.
I eat the oatmeal that was left over from yesterday.
Desayuno un plátano y nada más.
I have a banana and nothing else.

In your sentence it’s a general statement, so no article is needed.

What exactly does avena mean—oatmeal, oats, porridge?

Avena is the general word for oats.

In practice:

avena can mean:
- oats as a grain,
- oatmeal,
- oat porridge, depending on context.
In a sentence like Desayuno avena, the most natural interpretation is oatmeal/oat porridge for breakfast.

In Latin America, does plátano mean banana or plantain?

It varies by country, but common patterns are:

In much of Mexico, Central America, Caribbean, Andean countries:
- plátano often refers to plantain (the starchy kind you usually cook).
- banana or banano is more often the sweet, raw-eaten banana.
In some places, plátano is used more loosely and can mean any kind of banana-type fruit.

In your sentence Hoy desayuno avena con plátano, most Latin American readers would imagine a sweet banana, because that’s what people usually slice into oatmeal. But usage can be regional, so locals’ speech matters.

Why is it es simple y saludable and not está simple y saludable?

The verb ser (es) is used for inherent or characteristic qualities:

Es simple y saludable.
It is simple and healthy (by nature / as a general fact).

Estar (está) would sound more like a temporary state, which doesn’t fit well for a general description of your usual breakfast.

So here es is the natural choice because you’re describing the type of breakfast, not a temporary condition.

Does simple ever sound negative in Spanish, like “simple-minded”?

Yes, simple can be:

Neutral/positive: plain, uncomplicated, not elaborate
- Una receta simple = a simple (easy, straightforward) recipe.
- That’s the meaning in your sentence: simple = not complicated, easy to prepare.
Negative/colloquial: simple-minded, naïve, not very smart
- Es un poco simple. = He/She is a bit simple (not very sharp).

In the context of food or routines, simple is usually neutral or positive: simple y saludable sounds good.

What’s the difference between saludable and sano?

Both relate to health, and in many cases you can use either:

saludable: healthful, good for your health
- Una comida saludable = a healthy (good-for-you) meal.
sano:
- About people: una persona sana = a healthy person.
- About food/lifestyle: also used like healthy:
  - Una dieta sana, comida sana.

In your sentence:

Es simple y saludable.
Sounds very natural and common.
Es simple y sana.
Also correct, maybe slightly more common in some regions.

Both are fine; saludable is very transparent for learners.

What does the semicolon ; do here? Could I just use a period or a comma?

The semicolon links two closely related ideas that could be separate sentences but are kept together:

Hoy desayuno avena con plátano; es simple y saludable.

You could also write:

Hoy desayuno avena con plátano. Es simple y saludable. ✅ (very natural)
With a comma instead (…, es simple y saludable) is more informal and not ideal in careful writing, because each part has its own subject and verb.

So: semicolon or period are both fine; a period is probably more common in everyday writing.

Can Hoy desayuno avena con plátano describe a habit, or does it only mean “today”?

Because of hoy = today, the sentence focuses on this specific day:

Hoy desayuno avena con plátano.
→ Today I’m having oatmeal with banana.

To express a habit, you’d usually use an adverb like:

Siempre desayuno avena con plátano. = I always have oatmeal with banana.
Normalmente / Generalmente desayuno avena con plátano.
Todos los días desayuno avena con plátano.

The present tense desayuno alone can be habitual, but hoy makes it clearly about today.

Why are simple and saludable singular and not plural (simples y saludables)?

They’re describing one thing: your breakfast/meal.

Implicit subject of es = (Mi desayuno) es simple y saludable.
Desayuno (the meal) is singular, so the adjectives are singular too.

Adjectives only become plural if they describe a plural noun:

Mis desayunos son simples y saludables.
My breakfasts are simple and healthy.