Hi Shao, Expend and spend are synonyms (two words with the same meaning). However, expend is often used to describe an action with a negative consequence. Expend is frequently used to describe the utilization of a limited resource. "Shao became tired after all of his energy was expended." This means that Shao utilized all of his energy. Expend is rarely used to describe a purchase, unless it is a purchase made by an organization, company, or government. "ShaoCorporation expended all of its resources on chocolate parfait." This means that ShaoCorporation spent all of its money to buy chocolate parfait. "ShaoCountry expended a great deal of public revenue to provide free chocolate parfait to the citizens." Spend can be used in more situations. You can spend money (use money to pay for something), or you can spend energy/effort. "Shao spent a lot of time and effort to learn English." "Shao spent $5 to purchase chocolate parfait."

The word expend itself isn't used commonly in English. However, the word "expense" does. The most common deviation of "expend" would probably be "expensive." "This shirt is classy, but it's too expensive for me." "That meal is expensive." Spend is very common in relation to time and purchasing things. "How much money can you spend on your trip?" "I can spend $500 but, I plan on spending less than that." "How much did you spend?" "I only spent $475."

The only time I would used expend in conversation is in terms of energy. Eg. She expended a lot of energy whilst running

spend is much more common, and there are certain cases where spend is used, but expend is never used.For example: "How much did you spend on your new suit?" "How did you spend your afternoon?" "How do you spend your free time?" I don't think anyone would ever use expend in any of those sentences. Usually when I hear the word expend it is in the phrase "expend a great deal of time" or "expend a lot of effort", but spend would also work in both of these cases. Hope this helps!