If something is thinkable, a person can hold it in their mind as a real possibility — it can be imagined, considered, seriously entertained. Here is the honest thing about this word: in real English you will meet its opposite, unthinkable, ten or twenty times for every once you meet thinkable. Unthinkable is a very common everyday word ('war between them was unthinkable'). Thinkable on its own sounds bookish, and it turns up mostly in philosophy, in argument, or in a deliberate answering-back move — where a writer takes something that used to be unthinkable and says it has now become thinkable. That is really its home: it marks a change, the moment an idea crosses from impossible-to-imagine into imaginable. So it usually needs a 'now', a 'suddenly', or a 'once' near it to make sense. If you simply mean that something is possible or believable, say possible or believable; thinkable will sound strange there.

可想像的、想得到的、能被認真考慮的。日常英文幾乎只用反義的 unthinkable（不可思議、想都不敢想），thinkable 偏學術書面。