Prefiero enviar el documento por correo electrónico.

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Breakdown of Prefiero enviar el documento por correo electrónico.

• preferir: to prefer
• el documento: the document
• enviar: to send

Questions & Answers about Prefiero enviar el documento por correo electrónico.

Why does the sentence start with Prefiero and not Yo prefiero?

In Spanish, subject pronouns are often omitted because the verb ending already shows who is doing the action.

• Prefiero = I prefer
• The -o ending tells you it is I

So Prefiero enviar el documento... is completely natural.
You could say Yo prefiero..., but that usually adds emphasis or contrast, for example:

• Yo prefiero enviar el documento, no imprimirlo.
  = I prefer to send the document, not print it.

Why is it prefiero and not prefero?

Because preferir is a stem-changing verb. In the present tense, the e in the stem changes to ie in most forms.

So:

• yo prefiero
• tú prefieres
• él/ella prefiere
• nosotros preferimos
• vosotros preferís
• ellos prefieren

This is a very common pattern in Spanish.
The infinitive is preferir, but the yo form is prefiero.

Why is enviar left in the infinitive after prefiero?