What the sentence is about
Who or what are we saying something about?
Meaning
A sentence can tell us what someone or something does, what it is like, or what happens to it. That person or thing is the center of the statement, even when it does not act. Languages may use word order or verb forms to link it to the statement, and some need no separate word when it is understood. Topic is the chosen starting point for a message and can be a different participant.
How to spot it
Ask which person or thing is presented as doing something, being something, or having something happen to it, not just which one is mentioned first.
In your native language
English usually uses the subject to name the person or thing it makes a statement about. In an ordinary statement, the subject comes before the verb and can name a doer, someone in a state, or something affected by an action. It is not always the topic or the first phrase in the sentence.
Ella is tired.
Ella is the subject, but she is not carrying out an action.
My bag was found at the station.
The passive sentence presents the bag as the subject, not the person who found it.
After lunch, the kitchen was quiet.
The opening phrase gives the time; the kitchen is the subject.
In your learning language
Spanish links the subject to the statement through the verb's person and singular or plural form. The subject can be someone acting, something being described, or something undergoing an event. It need not come first or be expressed separately when the verb and context identify it.
Las dos ventanas están abiertas.
Both windows are open.
The plural verb matches las dos ventanas.
Me duelen los pies.
My feet hurt.
Los pies is the plural subject, so the verb is duelen; me identifies the person feeling the pain.
Tengo dos hermanos.
I have two brothers.
Tengo identifies the subject as I without a separate yo.
Learners whose language uses singular nouns after numbers may miss the plural verb needed with a Spanish plural subject. Learners whose language keeps subjects before verbs may mistake a person mentioned first for the subject.