Il tarlo rovina la venatura del legno.

Here tarlo means a woodworm or a wood-boring insect/larva that damages wood.

A useful extra note: tarlo can also be used figuratively in Italian to mean a nagging thought, obsession, or worry that keeps bothering someone. But in this sentence it is clearly the literal meaning.

Italian uses articles much more often than English.

So il tarlo can mean:

• the woodworm in a specific situation, or
• the woodworm in a more general, class-level sense

English often drops the article in general statements, but Italian usually keeps it. So Il tarlo rovina... sounds normal.

Also, il is used because tarlo is:

• masculine
• singular

Rovina is the 3rd person singular present tense of rovinare.

The subject is il tarlo, which is singular, so the verb must also be singular:

• io rovino = I ruin / damage
• tu rovini = you ruin / damage
• lui/lei rovina = he/she/it ruins / damages

So Il tarlo rovina... = The woodworm damages...

Venatura means the grain, veining, or natural patterned lines in a material, especially wood or stone.

In la venatura del legno, it refers to the visible natural grain pattern of the wood.

It is a feminine singular noun, which is why it takes la.

Because venatura is a feminine singular noun, so the correct definite article is la.

Italian articles must agree with the noun in gender and number:

• il tarlo = masculine singular
• la venatura = feminine singular

Also, Italian often uses the definite article where English may sound more natural without one. So la venatura is completely normal here.

Del is the contraction of di + il:

• di + il = del

So la venatura del legno literally means the grain of the wood.

This is the normal way to express that the grain belongs to or is a characteristic of the wood.

By contrast, di legno often means made of wood or wooden:

• un tavolo di legno = a wooden table

So here venatura del legno is the correct expression, not venatura di legno.

It can be understood either way depending on context.

Without extra context, Italian allows il + singular noun to express a general idea:

• Il tarlo rovina la venatura del legno can mean Woodworm damages the grain of wood

But in a real situation, it could also refer to a specific woodworm:

• That woodworm is damaging the grain of the wood

So the sentence works both as:

• a general truth
• a specific statement

Yes. This is the most neutral and standard word order in Italian:

subject + verb + object

• Il tarlo = subject
• rovina = verb
• la venatura del legno = object

Italian can sometimes change word order for emphasis, but this version is the straightforward, unmarked one.

Yes, but it would mean something slightly different.

• Il tarlo rovina il legno = The woodworm damages the wood
• Il tarlo rovina la venatura del legno = The woodworm damages the grain/pattern of the wood

The original sentence is more specific. It focuses on the wood's grain, not just the wood in general.

No. Rovinare is a transitive verb, so it can take a direct object without a preposition.

That is why you say:

• rovina la venatura

and not:

• rovina alla venatura
• rovina della venatura

So the structure is simply:

subject + rovinare + direct object

A few useful ones:

• tarlo → stress on the first syllable: TAR-lo
• rovina → stress on vi: ro-VI-na
• venatura → stress on tu: ve-na-TU-ra
• legno → gn sounds like the ny in canyon

So legno is pronounced roughly like LE-nyo, not like leg-no in English spelling terms.