Subject Pronouns

The subject pronoun which indicates who is doing the action generally precedes the verb. The forms are:
 

Nosotros and vosotros have feminine forms (nosotras, vosotras) when referring to a group made up entirely of women. If the group contains both males and females, the masculine form is used. Similarly, ellos can refer to a group made up of both men and women, while ellas refers to a group made up entirely of females.

The Use of Subject Pronouns

In English, the subject ‘it’ is always mentioned: ‘it is interesting,’ ‘here it is,’ ‘where is it?,’ etc. In Spanish, however, the subject pronoun ‘it’ is rarely, if ever, expressed. The verb stands alone, and the subject ‘it’ is understood: Es interestante, aquí está, ¿dónde está? etc.

Because most verb endings in Spanish tell who is doing the action, it is not necessary to use the subject pronouns in most cases: Trabajo en esta compañia (the verb ending -o indicates that the subject of the sentence is ‘I’). Only when there is a chance of confusion, or if the speaker wants to emphasize who is doing the action, is the subject pronoun used: Ella es española, pero él es norteamericano (the verb es can have as a subject ‘he’ and ‘she’); Yo quiero comer ahora (the yo is used only for emphasis, but is not necessary).