What is the Difference Between DEX and DeFi?

DeFi stands for Decentralized Finance, the direct opposite of Centralized Finance which is normally backed by intermediaries such as banks and financial institutions. It can be interpreted as the financial market without intermediaries. DEX is an entity whose role is mainly to support exchanges of crypto assets between crypto traders. To clarify this, you can view DEX, being an exchange booth where you can swap your currency to other currencies in the Centralized Finance world. Rather than being in the same category, DEX is more like one of the subsets of DeFi.