Practicability is the noun for how possible it is to actually do a plan in a real situation, with the time, money, people, and tools you have. A beautiful idea can have low practicability — it looks good on paper, but you cannot carry it out here and now. Committees, engineers, and lawyers like this word; it is formal. Though actually, many students mix it with practicality. Practicality is about whether something is sensible or useful in daily life ("these shoes have more practicality"). Practicability is narrower: can we do this at all, in these conditions? If a mountain rescue is not possible tonight because of the storm, that is a question of practicability, not of whether rescue is a "practical" habit.

可行性（眼前這個情況下做不做得成；不是「實用性」）