I have come across many people half understood the term “long” and “short”.
Most people know going long is equivalent to buying while going short is equivalent to selling.
But that is only half true.

Why use the term “long” and “short”?
Why not just use “buy” and “sell”?

The difference is here…

BUY vs LONG
When a trader buys into a counter, he could mean:

1. he is opening (entering/taking) a new long position
(he did not have any position before this);

or

2. he is closing a short position that he sold (opened/entered) earlier
i.e., he is buying back the counter that he sold earlier.

However, if the trader goes long on a counter, it is very clear he is opening (entering/taking) a new long position.
He is for sure not closing a short position.

SELL vs SHORT
When a trader sells a counter, he could mean:

1. he is opening (entering/taking) a new short position
(he did not have any position before this);

or

2. he is closing a long position that he bought (opened/entered) earlier
i.e., he is selling the counter that he bought earlier.

However, if the trader sells short a counter, it is very clear that he is opening (entering/taking) a new short position.
He is for sure not closing a long position.

Therefore, buy or sell would have 2 possible meanings whereas long or short has only 1 definite meaning.