If the number of shares is fixed and the amount of money chasing those shares increases then demand will drive prices higher. If the number of shares is fixed and the amount of money chasing those shares decreases then supply will drive prices down. The amount of money chasing a stock relative to the number of shares available determines the stocks price or market capitalization. If the amount of money is to increase that is chasing a stock it has to come from somewhere. An entities Money Market account can decrease while the entities Stock portfolio account increases. Once you admit that supply and demand determine a stock's price or market capitalization then you admit that saying money can be "in the market" or "out of the market". Yes, when money is in the market it is in the form of shares. When it is not in the market it is called cash. This cash can flow into the market (in increased buying or demand) or out of the market (in increased selling due to lack of demand). When cash flows into the market the price of stocks goes up and when cash flows out of the market stock prices go down.
You say it should not be said that way. But it is. that is common usage. Think of it this way. Your cash money passes through the stock market. When it is "in" the market it is in the form of stock.
I have cash money "tied up" in houses, guns, glassware, cars, furniture etc. I have that cash money in the form of different assets. I have some in cash. It is common English usage to say this and I think everyone knows what it means.
What do you count when you calculate "net worth"? Value of assets, cash and liabilities. It is measured in cash money.
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