La tensión del hilo afecta a la puntada.

Because del is the standard contraction of de + el.

• de el hilo → del hilo
• This only happens with de + el
• It does not happen with de + la, so you say de la puntada, not a contraction

So la tensión del hilo means the tension of the thread.

With afectar, Spanish very often uses a before the thing or person being affected.

So:

• afectar a la puntada = to affect the stitch

This a is part of the common verb pattern here. It does not mean to in the English sense. You should learn it as a natural construction:

• afectar a algo
• afectar a alguien

You may also sometimes see afectar algo, but afectar a is very common and sounds very natural here.

Spanish uses the definite article much more often than English, especially when talking about things in a general or technical way.

So Spanish says:

• La tensión del hilo afecta a la puntada

where English might say:

• Thread tension affects the stitch
• Thread tension affects stitching

In Spanish, the articles are perfectly normal here. You should not try to copy English article usage too closely.

Puntada usually means stitch in sewing: a single stitch or the quality/form of the stitch.

In this sentence, it likely refers to the stitch produced by the machine or sewing process. So the idea is that the thread tension affects how the stitch turns out.

This is different from some related words:

• punto = point, dot, stitch, knitted stitch, etc. depending on context
• costura = seam / sewing / stitching more generally
• puntada = a stitch, especially in sewing

Yes. Hilo means thread.

In sewing contexts, hilo is the normal word for thread. Depending on context, English might also say sewing thread, but in Spanish hilo is enough.

A learner might confuse it with similar words:

• hilo = thread
• hebra = strand / filament / a single strand of thread or hair

Here hilo is the normal choice.

Because the sentence states a general fact.

• afecta = it affects

The subject is la tensión del hilo, so the verb is third person singular:

• la tensión ... afecta

Spanish often uses the present tense for general truths, technical explanations, and instructions, just like English does:

• El calor afecta al metal
• La tensión del hilo afecta a la puntada

The subject is La tensión del hilo.

A useful way to see the structure is:

• La tensión del hilo = subject
• afecta = verb
• a la puntada = what is affected

So literally:

• The tension of the thread affects the stitch

Even though word order can be flexible in Spanish, this sentence follows a very straightforward pattern.

Because the noun tensión is grammatically feminine, so it takes la.

Many nouns ending in -ión are feminine:

• la tensión
• la presión
• la situación
• la información

So this is a helpful pattern to remember.

The accent mark shows where the stress goes:

• ten-SIÓN

Without the accent, the word would not follow normal Spanish spelling rules for where the stress should fall. The written accent tells you clearly that the stress is on the last syllable.

This is very common with nouns ending in -ión:

• tensión
• presión
• función

No. The h in Spanish is silent.

So hilo is pronounced roughly like EE-lo.

This is a very common feature of Spanish:

• hilo
• hola
• hora

All of these have a silent h.

Normally, no. La tensión del hilo is the natural phrase.

Spanish usually wants the article here:

• del hilo = of the thread

Saying de hilo would sound incomplete or unnatural in this context. It might only work in very specific set phrases, but not as the normal version of this sentence.

Not exactly.

• puntada = stitch
• costura = seam / sewing / stitching, depending on context

So in this sentence, puntada is more precise if you are talking about the actual stitch formation. If you used costura, the meaning would shift more toward the seam or sewing result in general.

Yes. This is a very direct and useful match.

• afectar = to affect

So:

• La tensión del hilo afecta a la puntada
  = Thread tension affects the stitch

This is one of the cases where the Spanish and English verbs line up quite closely in meaning.