In order to understand subject-verb agreement, you first need to know what a subject and a verb are.
Let’s start with subjects. When we use the word subject in a grammatical sense, we do not mean topic. How do we tell the difference? Consider the following sentence:
The man bought a new wallet.
Depending on many factors, the topic could be shopping, new wallets versus old ones or wallets. But the only doer or performer of an action in this example is the man.
Grammatically speaking, subjects perform an action. In Spanish, subjects may be singular or plural. Subjects are either nouns, which are names, labels if you wish, that identify a person, for instance John, he, I, they, you. A subject does not have to be a human being. It could be an animal, such as Rover, dog, elephant. It could be a plant, as in the rose. It could be a thing, like a corkscrew or a broom. It could even be an abstraction like love or envy. So, any and all nouns are eligible to be the grammatical subject of a sentence. Here are a couple of the examples above used as grammatical subjects:
John lives on 15 Avenue.
They clean the house on Saturdays.
Pronouns may also be grammatical subjects. Pronouns are words that stand in for nouns, and when a pronoun is used as a subject in Spanish, it will use its subject form. As you’ll learn in other lessons, there are other forms for other grammatical situations. As in English, in Spanish there are only a handful of subject pronouns.
By arranging these subject forms in a certain pattern, with the singular ones on the left and the plural ones on the right, we create a sort of pigeonhole arrangement. The pattern it creates has three boxes on the left for the three singular forms and three on the right for the plural ones. Also, each pigeon hole has its corresponding verb form. You can visualize this correspondence by imagining two of these identical pigeonhole patterns one on top of the other, one representing the subject pronouns and the other representing their corresponding verb forms. The bottom two boxes each contain three items: on the left, él, ella and usted; on the right, ellos, ellas and ustedes.
Furthermore, from top to bottom of this pattern, the boxes are identified as first, second and third person. This allows us to define more precisely what each box represents, as if using latitude and longitude. It’s a bit like playing the popular game Battleship.
The first person is defined as the person speaking. When singular, this person speaks for him or herself – I – found on the upper left. Immediately across from it, to the upper right, is the first-person plural, used when one person is speaking for a group – we. Note that in Spanish, if a woman is speaking for a group of women, she will use nosotras, not nosotros.
yo = I nosotros/-as = we
tú = you vosotros/-as = you
él = he ellos = they (masculine or mixed group)
ella = she ellas = they (feminine only)
usted = you ustedes = you
Although the pronoun it can be used as a subject in English, there is no corresponding use of any pronoun. When in English it would be the subject, in Spanish, it is understood; simply use the third-person verb form with no subject mentioned.
Looking at the chart closely, you’ll notice that there are four ways to say you in Spanish. Let’s start with tú. Tú is the form used between friends. Because it has a box all to itself, its corresponding verb form is unique to that box – and so the pronoun itself may be omitted because there can be no mistake as to who the subject is. Its corresponding plural, vosotros (or vosotras if the group is all female), is used only in Spain. Usted is the formal or polite form. In Latin America, because vosotros is not used, ustedes is the only way to say you in the plural. These two pronouns are often abbreviated in writing as Ud. and Uds. Also notice that yo and nosotros, like tú, have their own boxes.