El hongo apareció ayer.

Because hongo is a masculine noun in Spanish, so it takes el in the singular.

• el hongo = the mushroom / the fungus
• los hongos = the mushrooms / the fungi

The ending -o often suggests a masculine noun, and hongo follows that common pattern.

Apareció is the third person singular preterite form of aparecer.

That matches el hongo, which is he/she/it grammar-wise, so the verb has to be in the third person singular:

• yo aparecí = I appeared
• tú apareciste = you appeared
• él/ella/apareció = he/she/it appeared

Here, el hongo is the subject, so apareció means it appeared.

Spanish uses the preterite here because the sentence talks about a completed event at a specific time:

• ayer = yesterday

So El hongo apareció ayer presents the appearance as a finished event: it showed up yesterday.

If you used the imperfect, aparecía, it would sound more like:

• it was appearing
• it used to appear
• it appeared repeatedly/in the background

That does not fit as naturally with a single completed event on yesterday.

The accent mark shows where the stress goes: a-pa-re-CIÓ.

It is also a normal written feature of the third person singular preterite of many -er and -ir verbs:

• comió
• vivió
• apareció

Without the accent, the word would not follow standard Spanish spelling and pronunciation.

No. In standard Spanish, the h is silent.

So hongo is pronounced roughly like ONGO.

The sentence sounds approximately like:

el ON-go a-pa-re-SYÓ a-YER
(in standard Spain Spanish, the c before i sounds like the th in thin)

In many other varieties of Spanish, that same c sounds like an s.

In Spain Spanish, apareció is pronounced approximately:

a-pa-re-thyó

More carefully broken down:

• a
• pa
• re
• ció → in most of Spain, ci sounds like th
  • yo

So the stress is on the last syllable: a-pa-re-CIÓ.

If the learner is more familiar with Latin American pronunciation, they may hear it more like:

a-pa-re-syó

Both correspond to the same spelling.

Because aparecer only has the zc change in certain forms, especially the first person singular present:

• yo aparezco = I appear

But in the preterite, that zc does not appear:

• yo aparecí
• él/ella apareció

So apareció is the correct past form here.

El means the, while un means a/an.

So:

• El hongo apareció ayer = The mushroom appeared yesterday
• Un hongo apareció ayer = A mushroom appeared yesterday

Spanish uses the definite article when the speaker is referring to a specific mushroom already known from the context, or when it is treated as a particular one the listener can identify.

Here aparecer means something like:

• to appear
• to show up
• to emerge

With something like a mushroom, it often suggests that it came into view or sprang up.

So depending on context, English might translate it in different natural ways:

• The mushroom appeared yesterday.
• The mushroom showed up yesterday.
• The mushroom came up yesterday.

Yes. Spanish word order is more flexible than English.

You could also say:

• Ayer apareció el hongo.

This still means the same thing, but it puts more emphasis on ayer or sounds a bit more narrative.

The original order, El hongo apareció ayer, is very neutral and straightforward.

No. Ayer is normally used by itself, without a preposition.

So you say:

• ayer = yesterday

Examples:

• Llegó ayer. = He/She arrived yesterday.
• El hongo apareció ayer. = The mushroom appeared yesterday.

That is different from some other time expressions that may use prepositions.

Yes. Hongo can mean mushroom or fungus, depending on context.

In everyday contexts, many learners will first meet it as mushroom, but scientifically or more generally it can refer to a fungus.

So the exact English translation depends on the situation.