Often times, people will attempt to rationalize impulsive purchases by proclaiming that what they are buying is an investment. To define investment a little more tightly: producing material results with money — holding value, appreciation, or some other tangible result.
Luxuries, then, aren’t investments. Excluding a small amount of watches and articles of clothing, luxuries do not hold their value and depreciate.
Stocks, real estate, cryptocurrency, books, and people are just a few examples of investments. Stocks, real estate, and cryptocurrency all have the potential to hold their value and appreciate. Books, if you read the right ones, can have material impact on your life whether by providing you new information or changing the way you think. Investing in people is to say you provide others something of value you have, such as money or information.