📌Suit jacket comes with matching trouser and both are usually of the same material. They are the most formal of the 3. It has a closer fit which makes it less suitable for layering.
📌A blazer comes with no matching color of pants. Pair it with jeans. Slightly loose fit. Most blaizers for guys come in navy blue, other colours are really rare. It is less formal compared to a suit jacket but more formal compared to a sport jacket.
📌A sport jacket: Less formal of the 3 types. Most Casual of the 3. Loosely fit, hence supporting layering