El moho causa una merma.

In Spanish, it is very common to use the definite article with general nouns.

So el moho means mold in a general sense, not necessarily one specific patch of mold. Spanish often says:

• El moho causa una merma
• literally: The mold causes a loss/reduction
• naturally: Mold causes a loss/reduction

English often drops the article in general statements, but Spanish often keeps it.

Moho means mold or mildew, depending on context.

It is pronounced roughly MO-oh in standard Spanish. A few useful points:

• The h is silent.
• So you do not pronounce it like English moh-ho.
• The stress is on the first syllable: MO-ho.

Yes, moho is masculine, so it takes el:

• el moho

The ending -o often suggests a masculine noun, and here that pattern works. That is why you do not say la moho.

Merma means a reduction, decrease, loss, or shrinkage, depending on context.

In a sentence like El moho causa una merma, it usually refers to some kind of loss caused by mold, for example:

• loss of quality
• reduction in value
• decrease in quantity
• spoilage-related loss

In Spain, merma is quite a normal word in technical, commercial, agricultural, or food-related contexts.

Here una merma means a loss / a reduction.

Spanish often uses the indefinite article when introducing a singular countable result or effect:

• causa una merma = causes a loss / causes a reduction

If you removed una and said El moho causa merma, it might sound more generic or less natural in many contexts. Una merma is the standard, straightforward way to express it.

Causa is the third-person singular present tense of causar:

• yo causo = I cause
• tú causas = you cause
• él/ella causa = he/she/it causes

In this sentence, the subject is el moho, which is singular, so the verb must also be singular:

• El moho causa...

Because the subject, el moho, is singular.

Spanish verbs must agree with the subject:

• El moho causa = singular subject + singular verb
• Los mohos causan = plural subject + plural verb

So if you changed the sentence to talk about multiple kinds or instances of mold, you would say:

• Los mohos causan una merma

Yes. Provoca and causa are both possible here.

• El moho causa una merma
• El moho provoca una merma

Both mean something like Mold causes a loss/reduction.

A small nuance:

• causar can sound slightly more neutral or formal
• provocar can sometimes feel a bit more like bring about or trigger

But in many contexts, both work well.

This is the most neutral Spanish word order:

• subject + verb + object

So:

• El moho = subject
• causa = verb
• una merma = direct object

This is the normal, unmarked order for a simple statement in Spanish, just like Mold causes a loss in English.

It is fairly common, but it is not one of the very first words learners usually meet.

You are especially likely to see merma in contexts like:

• food production
• storage
• agriculture
• business
• manufacturing
• quality control

It often refers to measurable loss, waste, reduction, or shrinkage. In very everyday English, you might sometimes translate it more loosely depending on context, rather than always using the exact word loss or reduction.

Yes, it can.

El moho causa una merma sounds fairly neutral-to-technical, especially because of merma. You might find this kind of sentence in:

• reports
• product descriptions
• technical manuals
• food safety discussions
• agricultural or storage contexts

In casual conversation, a speaker might choose a simpler or more specific expression depending on what exactly is being lost.

Yes, a few common ones:

• moho: the h is silent
• causa: pronounced roughly KAU-sa, not like English cause
• merma: pronounced roughly MER-ma, with a tapped Spanish r, not an English-style long r

Also remember:

• Spanish vowels are usually pure and short
• each written vowel is pronounced clearly: mo-ho, cau-sa, mer-ma

You would change both the subject and the verb:

• Los mohos causan una merma = Molds cause a loss
• Los mohos causan mermas = Molds cause losses

Which version you choose depends on meaning:

• una merma = one general loss/reduction
• mermas = multiple losses/reductions

The key grammar point is that the verb must agree with the plural subject:

• el moho causa
• los mohos causan