Subject pronouns (pronombre personal sujeto) are the words that replace the subject (the person or thing doing the action) in a sentence. Spanish subject pronouns reflect the gender, number, and person of the noun they replace. They include:

Unlike English, where only the third-person singular pronouns are gendered, Spanish has a more extensive system of gendered pronouns.
In third-person singular, "él" is used to refer to a man, while "ella" is used when talking about a woman. Here are some examples:

In first person plural, "nosotros" is used to refer to a group of masculine subjects that includes the speaker. Additionally, when the group consists of a mix of male and female subjects, "nosotros" is the correct form. "Nosotras" is used when the group consists entirely of female subjects. For example:

Similarly, in the third-person plural, "ellos" is used for all-male or mixed gender groups while "ellas" is used to refer to an all-female group. Take a look at the examples:

For second person singular, Spanish has two forms:

In Spain, "vosotros" (masculine) and "vosotras" (feminine) are used as the second-person plural subject pronouns in informal contexts and "ustedes" is saved for formal occasions. Latin American Spanish, however, uses "ustedes" as both formal and informal terms of address for the second-person plural.

In Spanish, the subject pronoun is often dropped and the verb inflection clarifies the subject.

However, in some cases the subject pronoun can be made explicit for clarity or emphasis. For example, the third-person singular conjugation of the verb can be applied to both "él" and "ella." So, in order to avoid confusion, the subject pronoun can be explicitly mentioned.