A jacket is a light, outer covering of clothing worn when it's cool outside. The difference between a jacket and a coat is a jacket is lighter, but sometimes these two words are used in exactly the same way.
Sometimes I wear a jacket in the classroom.
A jacket is more casual than a suit coat.
She wears a jacket when it's cool outside.
A jean jacket is a popular choice of clothing for the spring of the fall.
Skiers wear ski jackets when they are skiing.
A life jacket can help keep you safe when you are on a boat or in the water. This is also called a life vest.
A yellow jacket is a type of wasp that will sting you if you bother it.