Your competitors are all solving the same problem
Entrepreneurs often define their competitors narrowly. They may only look at others who are solving the same problem in the same way. The better approach is to think about competitors as everyone solving the same problem even if they’re doing it in a radically different way.
For example, when you look at the addressable market for Seek a narrow definition would be anyone looking for jobs or staff online. A broad definition would be any way that people find jobs or staff - online, through a notice in a shop front window, word of mouth or networks. The broader definition includes all of the real competitors because many jobs are still filled through a job being posted on the window of a retail store or word of mouth. If you defined the competition too narrowly then you would eat into the true size of the market opportunity.
Another example is a company Square Peg recently invested in, Athena. Athena is competing in the mortgage market in Australia - a $1.7 trillion market with $440 billion of new mortgages written every year. While many non-bank players in the mortgage market are operating in a particular part of the stack - they may just do origination, lead generation or be a broker - Athena sees their competitor set as everyone trying to solve the problem of originating and financing home loans to homeowners.