Prefiero una copa de tinto.

Because preferir is the infinitive, and prefiero is the first-person singular present tense form: I prefer.

This verb is also a stem-changing verb:

• preferir → prefiero
• The e in the stem changes to ie in many present-tense forms.

Present tense:

• yo prefiero
• tú prefieres
• él/ella/usted prefiere
• nosotros/nosotras preferimos
• ellos/ellas/ustedes prefieren

So prefiero is the correct form for I prefer.

Because Spanish often drops subject pronouns when the verb already shows who the subject is.

• Prefiero already tells you the subject is I
• So yo is usually unnecessary

You would add yo only for emphasis or contrast, for example:

• Yo prefiero una copa de tinto, pero ella prefiere cerveza.

In normal conversation, Prefiero una copa de tinto sounds natural.

Because copa is a feminine noun, so it takes the feminine article una.

• una copa
• la copa

This is something learners often need to memorize with each noun:

• el vaso
• la copa
• el vino

Even though tinto is masculine, the article agrees with copa, not with tinto.

Because Spanish commonly uses the pattern:

container + de + contents

So:

• una copa de vino
• un vaso de agua
• una taza de café
• una botella de cerveza

Here, copa is the container, and tinto is what is in it.

So de works like of in English:

• a glass of red wine

Because in many Spanish-speaking contexts, tinto can be used by itself to mean red wine, especially when the word vino is understood.

So these can be similar:

• una copa de tinto
• una copa de vino tinto

The shorter version is natural in many situations, especially when talking about drinks.

However, there is an important regional note:

• In many places, tinto means red wine
• But in Colombia, tinto very often means black coffee

So in Latin America, this word can be regional. If you want to be completely clear everywhere, vino tinto is safer.

Yes. In Spanish, adjectives sometimes become nouns when the main noun is understood.

Here, tinto originally describes vino:

• vino tinto = red wine

But if vino is understood, speakers can simply say:

• un tinto
• una copa de tinto

This is similar to how English sometimes says things like:

• the red when the red wine is understood

So tinto is acting like a shortened form of vino tinto.

It can be natural, but it usually sounds more like stating a preference than making a direct request.

It works especially well:

• when choosing between options
• when responding to a question
• when contrasting with another drink

For example:

• ¿Blanco o tinto?
• Prefiero una copa de tinto.

If you are ordering more directly, you might also hear:

• Quisiera una copa de vino tinto.
• Me gustaría una copa de vino tinto.
• Para mí, una copa de vino tinto.

So prefiero is correct, but it is not always the most typical standalone ordering phrase.

These expressions have different tones:

• Prefiero = I prefer
  • expresses a preference, often compared to something else
• Quiero = I want
  • direct and common, but can sound blunt depending on tone
• Me gustaría = I would like
  • polite and very common
• Quisiera = also polite, often a bit more formal

So:

• Prefiero una copa de tinto = I prefer a glass of red wine
• Quiero una copa de tinto = I want a glass of red wine
• Me gustaría una copa de tinto = I’d like a glass of red wine

Because copa usually means a stemmed glass, especially one used for wine, while vaso means a regular drinking glass or tumbler.

Typical pairings:

• una copa de vino
• un vaso de agua
• un vaso de jugo

So if you are talking about wine, copa is the normal choice.

Yes, but the meaning shifts slightly.

• Prefiero vino tinto
  = I prefer red wine
  This sounds more general, like a category preference.

• Prefiero un tinto
  = I prefer a red wine / a glass of red wine
  This can work in context, though it depends on regional usage.

• Prefiero una copa de tinto
  = I prefer a glass of red wine
  This is more specific about the serving.

So the sentence with una copa emphasizes the amount or serving format.

A little, yes. Spanish word order is often more flexible than English, but the most neutral version here is:

• Prefiero una copa de tinto.

Other versions are possible for emphasis:

• Yo prefiero una copa de tinto.
• Una copa de tinto prefiero.
  This is much less neutral and sounds marked or literary.

So learners should usually stick with:

• Prefiero una copa de tinto.

Not only, but prefiero often suggests an explicit or implicit comparison.

For example, it may imply:

• instead of white wine
• instead of beer
• instead of another option being discussed

Even if the comparison is not stated, Spanish speakers often understand one is implied:

• Prefiero una copa de tinto
  = I prefer a glass of red wine, rather than something else

So the sentence feels especially natural in a context where choices are being considered.