The natural sugar found in milk — cow's milk, human milk, and the milk of other mammals. It is what makes plain milk taste faintly sweet.

The natural sugar天然糖分 found in milk存在於奶裡的——cow's milk, human milk, and the milk of other mammals牛奶、人奶，還有其他哺乳動物的奶。It它 is what makes是讓...的原因 plain milk原味牛奶 taste faintly sweet嚐起來帶點淡淡甜味。

Most students meet this word not in biology class but on food labels and in the phrase 'lactose intolerant': many adults, and a very large share of people in East Asia, stop making enough of the enzyme that breaks lactose down, so milk gives them stomach pain, gas, or diarrhoea. That is why supermarkets here sell 無乳糖 milk, and why 'lactose-free' appears on so many cartons.

Most students大部分學生 meet this word遇到這個字 not in biology class不是在生物課上，but on food labels而是在食品標示上，and in the phrase 'lactose intolerant'還有在「lactose intolerant(乳糖不耐)」這個詞裡：many adults很多成年人，and a very large share of people in East Asia還有東亞地區很大一部分的人，stop making enough of the enzyme不再製造足夠的酵素 that breaks lactose down用來分解乳糖的，so milk gives them stomach pain, gas, or diarrhoea所以喝牛奶會讓他們肚子痛、脹氣，或拉肚子。That is why這就是為什麼 supermarkets here sell 無乳糖 milk這裡的超市會賣無乳糖牛奶，and why 'lactose-free' appears on so many cartons也是為什麼「lactose-free」會出現在這麼多包裝上。

The word itself is neutral and technical — it names the substance, not the problem. Note that lactose intolerance is not a milk allergy: intolerance is a digestion problem and unpleasant; a milk allergy is the immune system reacting and can be dangerous.

The word itself這個字本身 is neutral and technical是中性、專業的——it names the substance它指的是這個物質，not the problem而不是那個問題。Note that要注意，lactose intolerance乳糖不耐 is not a milk allergy不是牛奶過敏：intolerance不耐 is a digestion problem and unpleasant是消化上的問題，會讓人不舒服；a milk allergy牛奶過敏 is the immune system reacting是免疫系統在反應，and can be dangerous而且可能會有危險。