Ich bin müde.
English: I am tired.
Subject pronouns replace names at the start of a sentence and connect to helper words like 'sein' and 'haben' in German.
Use subject pronouns as the sentence subject before the verb.
Ich bin müde.
English: I am tired.
Sie sind Freunde.
English: They are friends.
Er weiß es nicht.
English: He does not know.
Es ist kalt.
English: It is cold.