Hearthstone is constantly adding new keywords to improve gameplay and give players new opportunities to express their skillset.
In the latest United in Stormwind expansion, the keyword Tradeable was added, which confused some players on how to use and benefit from it. At the time of writing, there are 13 usable Tradeable cards.
A card with the Tradeable keyword is a card that can be played normally just like any other card, but with one extra effect. For the cost of one mana, you can drag it into your deck to draw a new card and shuffle the Tradeable card into your deck. This action is called a Trade.
If you want to be certain that you can use this effect, just click on a Tradeable card and it should flash green to note that you can Trade it. On top of this keyword, these cards have the recycling icon below their mana cost for another reminder that they can be Traded.
These cards can be Traded indefinitely as long as your deck is not empty. If your deck is empty, then you can no longer use this effect and will be forced to play it regularly. The Trade effect is considered as a normal draw and will trigger other cards that give some benefits based on drawing cards.
