If an actor forget his word, he have to improvise.
演员要是忘记台词，那就只好即兴现编。
The pianist forgot his music and had to improvise (the accompaniment).
弹钢琴的人把乐谱忘了, 只好即兴伴奏.
As we've not got the proper materials, we'll just have to improvise.
我们没有弄到合适的材料, 只好临时凑合了.
