strange question really. do you mean when to use i and when to use i am? I is a subject pronoun, I am is a subject pronoun+a verb to' be' in the present simple tense i like tea. i go to the beach in summer. i always work hard. i am tired. i'm thirsty. i am a teacher. i'm happy to see you here. So. I is subject, but I am is a subject and verb

أنا .....صفة I am big أنا كبير أنا .....خبر I am a girl أنا بنت