A common noun is a word that names people, places, things, or ideas. They are not the names of a single person, place or thing.
A common noun begins with a lowercase letter unless it is at the beginning of a sentence.
man, girl, boy, mother, father, child, person, teacher, student
cat, dog, fish, ant, snake
book, table, chair, phone
school, city, building, shop
love, hate, idea, pride