If you are going to attend any important event, the most important thing that you should cater for is the dress.
You may need a blazer or a suit jacket, depending on the nature of the function. Since there is a lot of difference between these two garments, one needs to be really mindful when preparing for a specific occasion. Things are surely a little confusing, but you can differentiate the blazer and the suit just by knowing their simple characteristics.
Normally, a suit jacket cannot be bought separately, as it comes with pants and sometimes a vest. Blazers, on the other hand, are exclusively available in the market. The fabric used for these two items is also different, with the one used in blazer being thicker.
A suit jacket is more formal, and comes in various colours. On the contrary, a blazer generally has very traditional colours, such as dark blue, dark green, red, white, navy or ivory.
The use of buttons is another difference. A suit jacket always has matching and formal buttons. In blazers, you will mostly see gold, black or silver buttons. One can wear any pants with a blazer, even jeans can compliment it. However, a suit jacket can be worn only with the matching pants. Furthermore, one cannot wear a casual T-shirt with a suit.
Nick Sullivan, the expert at Esquire, defines the blazer as a jacket that has sleeves and lapels, and can be worn with any trouser, matching or not. The suit jacket on the other hand has been defined as a formal garment made of smooth and fine fabric.