1. The idea of antigravity was originally suggested by Einstein as a kind of add-on to his General Theory of Relativity. 反引力的概念最早是由爱因斯坦作为一种附加理论在相对论中提出来的。
2. If the dominant outfit is afraid a new add-on will make its own technology redundant, it will not deal with competitors on any terms. 如果占统治地位的公司担心新的附加物会使自己的技术冗长，那它在任何条款下都不会与竞争者进行交易。
3. The Label Shapes add-on cannot continue because there are no shapes on the drawing page. Add shapes to the drawing page and try again. “给形状加标签”加载项无法继续运行，因为绘图页上没有任何形状。请向绘图页添加形状，然后重试。
英英解释
n.
1. a component that is added to something to improve it
2. a supplementary component that improves capability v.
1. make an addition
2. add to the very end
