Trigger (off) (verb)

●To make something happen.（觸發，激起）

Examples:　　

1.The news of his death triggered more violence.

2.The racial killings at the weekend have triggered off a wave of protests.

Variable (noun)

●An element, feature, or factor that is liable to vary or change.（變數，可變因素）

Examples:　　

1.There are too many variables involved to make any meaningful predictions.

2.Purchase decisions could be made on the basis of price, delivery dates, after-sales service or any other variable.

The game is not worth the candle (idiom)

●If you say that the game is not worth the candle, you mean that something is not worth the trouble or effort needed to achieve or obtain it.

（不值得，得不償失）

Examples:　　

1.The local council considered the construction of a new power grid throughout the county, but because it would cost millions and only marginally increase efficiency compared to the current infrastructure, they decided that the game wasn't worth the candle.　　

2.They may find that aggressive expansion is not worth the candle.

Break out (phrasal verb)

●If something dangerous or unpleasant breaks out, it suddenly starts.（爆發，突然發生）

Examples:　　

1.War broke out in 1914.　　

2.Fighting has broken out all over the city.

Return On Investment (ROI) (economic term)

●投資回報率（ROI）是指通過投資而應返回的價值，即企業從一項投資性商業活動中得到的經濟回報。投資回報率的計算公式：

　　　　ROI=年利潤／投資總額×100%。