>>300216The difference between your examples and the perch v. sunfish example is the context.
In your examples the context is very clear.
>I put gas in my car and will purchase it with cash."Gas" could refer to...
A. A state of matter, or
B. Gasoline/Petrol
Because in this case you are putting "gas" in your car it is obvious that "gas" refers to gasoline.
Likewise, "car" in this situation also has a clear context.
"Car" could refer to...
A. An automobile, or
B. A railway car
Because you are filling it with gasoline, it is obvious it is not a railway car because railway cars do not need fuel(locomotives do but they don't run on gasoline).
Finally, "cash" in this case doesn't really work like the other two.
> ...cash (instead of bills and coins)."Cash" is literally is defined as...
cash /kaSH/
noun: cash
1. money in coins or notes, as distinct from checks, money orders, or credit.
Now lets look at the context for the perch v. sunfish.
The context is no longer clear however when talking about fish.
>I caught some perch at the lake today. They sure had a lot of blue gills on them and no vertical stripes. Since we are talking about fish, we know that perch broadly refers to fish from the Percidae family and fish well known as perch are from the genus Perca (Yellow, European and Balkhash Perches).
The sentence confuses our reader! As it should because the speaker is taking about fish from the Centrarchidae faimly. The two fish are vastly different and in this context "perch" makes no sence.
Furthermore, it can become even more confusing when the fisherman actually did catch both yellow perch and bluegills and refer to them both as perch.
Hope this cleared some things up.
