Smog is dirty air over a city — air so full of smoke and chemicals from cars, factories and burning that it hangs there like a grey or brown fog. You can see it: the buildings a few streets away go soft and pale, and the sky loses its edge. On bad days it stings your eyes and throat, and people with asthma are told to stay inside.

Smog指的是 is dirty air over a city城市上空的髒空氣 — air so full of smoke and chemicals裡面充滿了煙和化學物質 from cars, factories and burning來自汽車、工廠和燃燒 that多到 it hangs there像一層 like a grey or brown fog灰色或棕色的霧一樣籠罩在那裡. You你 can see it可以親眼看到: the buildings a few streets away幾條街外的建築物 go soft and pale會變得模糊、發白, and而 the sky天空 loses its edge也失去了輪廓. On bad days狀況差的日子裡, it它 stings your eyes and throat會刺痛你的眼睛和喉嚨, and而 people with asthma有氣喘的人 are told to stay inside會被叮嚀待在室內.

It is a noun, and usually uncountable — "there was smog all week," not "a smog" — though older writing does say "a smog" for one particular episode.

It這 is a noun是名詞, and而 usually uncountable通常是不可數的 — "there was smog all week,"是『there was smog all week（整週都有smog）』 not "a smog"不是『a smog』 — though不過 older writing比較舊的寫法 does say會用 "a smog"『a smog』 for one particular episode來指某一次特定的事件.

Two kinds get talked about. The old kind, sometimes called winter smog, is coal smoke trapped by cold damp air; London was famous for it, and in 1952 it killed thousands of people in a few days. The newer kind is photochemical smog: sunlight cooks car exhaust into ozone, and it looks brownish and gets worse on hot afternoons — that is the Los Angeles, Bangkok and Delhi kind.

Two kinds常被談到的有兩種 get talked about. The old kind比較舊的一種, sometimes called winter smog有時叫做winter smog（冬季霧霾）, is coal smoke trapped by cold damp air是煤煙被又冷又濕的空氣困住形成的; London倫敦 was famous for it以前就以此聞名, and而 in 1952 1952年 it killed thousands of people in a few days還在短短幾天內奪走了好幾千條人命. The newer kind比較新的一種 is photochemical smog是photochemical smog（光化學煙霧）: sunlight cooks car exhaust into ozone陽光把汽車廢氣『煮』成臭氧, and而 it looks brownish看起來偏棕色 and gets worse on hot afternoons天氣熱的下午會更嚴重 — that is the Los Angeles, Bangkok and Delhi kind這就是洛杉磯、曼谷和德里那種.

In Taiwan people mostly meet the word through news about winter air in the west of the island, though what is actually measured now is usually PM2.5 rather than smog as such. Note that everyday speech has stretched the word: many speakers now say smog for any bad air pollution you can see, even a haze that is really dust or farm burning.

In Taiwan在台灣, people大家 mostly meet the word大多是認識這個詞 through news about winter air透過...冬季空氣的新聞 in the west of the island在西部, though不過 what is actually measured now現在實際被拿來測量的 is usually PM2.5通常是PM2.5, rather than smog as such而不是smog本身. Note that要注意的是, everyday speech日常說法 has stretched the word已經把這個詞用得更寬鬆了: many speakers現在很多人 now say smog都說smog for any bad air pollution you can see只要是看得到的空氣污染, even就算 a haze其實是霾 that is really dust or farm burning是揚塵或燒田引起的也一樣.