This is engine talk. Inside an engine there is a piston that slides up and down inside a tube, and each single up or down movement is called a stroke.

This is engine talk這是講引擎的用語. Inside an engine there is a piston that slides up and down inside a tube引擎裡面有一個活塞在一根管子裡上下滑動, and each single up or down movement is called a stroke每一次上或下的動作就叫做一個stroke（衝程）

A two-stroke engine finishes its whole cycle — pull in fuel, burn it, push out the smoke — in just two of those movements, one up and one down. A four-stroke engine takes four.

A two-stroke engine finishes its whole cycletwo-stroke engine完成整個循環 — pull in fuel, burn it, push out the smoke吸入燃料、燃燒、排出廢氣 — in just two of those movements, one up and one down只靠那兩個動作，一上一下. A four-stroke engine takes fourfour-stroke engine則要四個動作

Because a two-stroke fires every single time round, it gives a lot of power for its size and weight, and it is simpler and cheaper to build; that is why you find them in scooters, small motorbikes, chainsaws, lawnmowers and outboard boat motors. The trade-off is that they burn oil mixed into the fuel, so they smoke, smell, and pollute badly — that high buzzing sound and the blue smoke from an old scooter is a two-stroke.

Because a two-stroke fires every single time round因為two-stroke每轉一圈就點火一次, it gives a lot of power for its size and weight以它的體積和重量來說馬力算大, and it is simpler and cheaper to build而且構造簡單、成本便宜; that is why you find them in scooters, small motorbikes, chainsaws, lawnmowers and outboard boat motors這就是為什麼機車、小型摩托車、電鋸、割草機和船外機上都看得到它. The trade-off is that they burn oil mixed into the fuel代價是它們燒的燃料裡混了機油, so they smoke, smell, and pollute badly所以會冒煙、有味道、污染很嚴重 — that high buzzing sound and the blue smoke from an old scooter is a two-stroke老機車那種尖銳的嗡嗡聲和藍煙，就是two-stroke

This matters in Taiwan: the government spent years paying people to scrap old two-stroke scooters (二行程機車) because of air pollution, so you may know the Chinese word from the news even if the English is new.

This matters in Taiwan這在台灣很有關係: the government spent years paying people to scrap old two-stroke scooters (二行程機車) because of air pollution政府因為空氣污染，花了好幾年補助大家淘汰舊的two-stroke scooters（二行程機車）, so you may know the Chinese word from the news even if the English is new所以你可能從新聞裡就認得這個中文詞，即使英文是新的

Use it before a noun — 'a two-stroke engine', 'a two-stroke scooter' — or on its own as a noun for the engine itself: 'it's a two-stroke'.

Use it before a noun放在名詞前面用 — 'a two-stroke engine', 'a two-stroke scooter''a two-stroke engine'（二行程引擎）、'a two-stroke scooter'（二行程機車） — or on its own as a noun for the engine itself或單獨當名詞指引擎本身: 'it's a two-stroke''it's a two-stroke'（這是個二行程的）