You actually answered your own question there OP. Yes it was those who buy and hold are mainly the investors, however I have heard already that there are traders who can wait too for a while before trading in order for them to not experience a loss or a big loss and then they can also earn a profit by doing this simple trick. That being said, they can be investor too but maybe short-term investor is the precise term for them.

I also like to say this that in general, when a person buy or avail something like a service, etc... and as long as they are pretty useful, that can also be said as an investment, so they can be called as an investor too.

I disagree with that because it's not only about buying but it's about the intention behind that purchase. If you are buying Bitcoin today and selling it tomorrow to get a small percentage of profit from it, you are not an investor, but you are a trader; but if you buy Bitcoin today and intend to hold it for some time until its price goes up to a certain point and then you sell, then you are an investor because investors usually aim for long-term profits and gains and don't focus on short-term.

A trader would buy and sell assets within short-term for small amounts of profit and they wouldn't hold them for long because they aren't buying with the intention of holding and that can't be considered investing. If traders would be called investors as well, we wouldn't need a different word for it.

Traders are just those who hold for a while, waiting for the perfect timing to sell their coins. But it won't take so long. But investors take several months to years holding their coins before they sell them. To the question of whether a trader can be an investor? It will happen if they are not an active trader. It was just the time difference that made someone an investor or a trader. But to generalize the situation. Those who hold long (not just days) are considered investors. I could be wrong to others, but this is my opinion.

They're involved in the finance system, traders simply focus on short term target and they need to risk careful

Investors are more focused on long term goals they buy and hold for a period of time when it is suitable for them

There is no point trying to make trader and investor look somehow. A trader is a trader, and an investor is an investor. The difference is pop and plain, investors buy Bitcoin and HODL for a long period of time and sell for profit . it could be bought in bear season and sold in the bulling, and it could also be bought in-between bull and Bear season and sold at any given time provided it's a long time investment. Which trader in order hands buy and sell Bitcoin to make profit but the traders mindset is to buy instantly and sell instantly without considering the amount of profit made. Both buy and sell for profit but the time frame is what makes the both to be different.

If traders can be called investors, then are investors can be considered as traders too? For me there is a difference between the two.

A trader's mindset focuses on the short term profit. They carefully analyze the market sentiment and predict it's movement in a short amount of time. Most of them studies technical analysis to read the market to become a profitable trader.

While an investor is aiming for long-term profit. Their goal is to accumulate and hold it for many years. You don't need some chart-reading skills here. Knowing DCA strategy is already enough to be a wise investor.

There's a big gap between investors and traders, Investors only buy one particular coin which is Bitcoin then hold it for a very long period to make profit in the future whereas traders don't rely on one particular coin, they speculate the price of different coins or stock then use help of different market analysis to buy and sell it then stand a chance of making profit in a short period and it's more risky compared to what Investors do.

 An investor goal is to buy and hold Bitcoin for the future and selling it within a time frame that's not 4 years and above is like imitating a trader such person is not a real investor, to make it more understandable just know that investors buy and hold Bitcoin for a longer period while a traders goal is short-term.

In my view, investors and trading two different options, although the two main goals are the same as 'profits' but investors are more directed to investing in the long term, while short -term trade Meaning: You can buy Bitcoin and store 5-10 years to generate certain profits, trading selling and buying in a short time.

CONCLUSION Trade and investors expenditure activities to generate profits, only the way it works is different, the same is the same.

Investors are those persons that buys and hold Bitcoin for a long-term of 4 years-10 years or more, they focus on buying alone on building their wealth gradually, after which they have reached their holding peak may decide to sell or still continue to accumulate and HODLing if they wish while Traders are those persons that buys Bitcoin for a period of short-term, ranging from minutes to months in other to sell them to make profits, but those profit tends to be smaller compared to that of investment.
Traders feels investing in Bitcoin is more risky than trading, for some persons that have been involved in trading before starting investment knows that investing is more safer and less in terms of risk.
Trading is more risky than investing, and investor are not traders, investors builds up their investment that turns into wealth after a long period of time, traders sell off their wealth immediately.

Traders in Bitcoin cannot be called investors. I think they is a separate definition for both of them as they do not mean the same thing. In my own opinion, an Investor in Bitcoin is a long term holder that consistently buy and accumulate Bitcoin,he  keep stashing enough into his investments portfolio until he reaches his over accumulation status,while Hodling for a long term for at least, a period of 4-10 years. However, a trader in bitcoin only buys Bitcoin  to resell it in a short intervals for profits. They both share something in common and that's is the goal to generate profits. I think traders method of making profits is risky and doesn't guarantee safety of funds when trading as the trader might like lose everything in a spot if things goes wrong.