La lentilla mejora la nitidez.

Yes. Lentilla can mean lentil, but in Spain it also very commonly means contact lens.

In this sentence, the context makes contact lens the only sensible meaning, because mejora la nitidez fits vision/optics, not food.

So:

• una lentilla = a contact lens
• las lentillas = contact lenses

If you want to be extra explicit, you can also say lente de contacto, but in Spain lentilla is very normal in everyday speech.

Spanish uses the definite article the more often than English does.

Here:

• La lentilla = the contact lens or sometimes a contact lens / the lens in question, depending on context
• la nitidez = sharpness / clarity

With abstract nouns like nitidez, Spanish often keeps the article where English might not:

• mejora la nitidez = improves sharpness / improves the sharpness

So even if English might sound more natural without the, Spanish often still uses la.

Mejora is the third-person singular present tense of mejorar.

The subject is la lentilla, which is singular, so the verb must also be singular:

• mejorar = to improve
• la lentilla mejora = the contact lens improves

A quick comparison:

• La lentilla mejora la nitidez. = singular
• Las lentillas mejoran la nitidez. = plural

Because mejorar can directly take an object in Spanish.

So you say:

• mejorar algo = to improve something

That is why:

• La lentilla mejora la nitidez.

and not:

• mejora a la nitidez
• mejora de la nitidez

Those would be incorrect here.

Nitidez means sharpness, crispness, or clarity, especially in visual contexts.

It is often used for:

• eyesight
• image quality
• focus
• optics

So in this sentence it suggests that the contact lens makes vision or the image appear sharper.

It is more specific than some other words:

• claridad = clarity in a broader sense
• nitidez = sharp visual definition

Yes. Lente de contacto is correct and fully understandable.

However, in Spain, lentilla is extremely common in everyday speech and often sounds more natural in informal, normal conversation.

So both work, but the feel is a little different:

• lentilla = everyday Spain Spanish
• lente de contacto = more explicit, sometimes a bit more formal or technical

Because nitidez is usually treated as an uncountable abstract noun, like clarity or sharpness in English.

You normally talk about it as a general quality:

• la nitidez
• más nitidez
• menos nitidez

The plural nitideces exists, but it is much less common and would only be used in special contexts.

It could be either, depending on context.

La lentilla can refer to:

1. one specific contact lens
2. the contact lens as a type of thing, in a general statement

For example:

• If an optician is discussing one lens, it may mean this lens improves sharpness.
• In a general explanation, it may mean the contact lens improves sharpness as a concept.

If you clearly mean contact lenses in general, you could also say:

• Las lentillas mejoran la nitidez.

A simple pronunciation guide:

• lentilla ≈ len-TEE-ya
• nitidez ≈ nee-tee-DETH in most of Spain

A few helpful notes:

• In most of Spain, z in nitidez is pronounced like the th in think
• The stress in lentilla falls on -ti-
• The stress in nitidez falls on the last syllable -dez

In much of Spain, ll is pronounced like a y sound.

It can correspond to either in English.

Spanish often uses a straightforward verb + noun structure where English may prefer a more natural paraphrase.

So these are all possible translations depending on context:

• improves sharpness
• improves the clarity
• makes vision sharper
• makes the image clearer

The Spanish itself is neutral and fairly direct.

Yes, especially in an optics, medical, or product-description context.

It sounds natural if you are talking about:

• vision correction
• lenses
• image quality
• optical performance

In everyday speech, someone might also say:

• La lentilla te hace ver mejor.
• La lentilla mejora la visión.

Those are a bit less technical. Mejora la nitidez sounds slightly more precise or technical.