我觉得frying potatoes是还没有炸好的土豆，后者是已经炸好的。
牛津高阶英汉双解词典
fry 1
1 / fra?; fra?/ v (pt, pp fried / fra?d; fra?d/)
[I, Tn] cook (sth) or be cooked in boiling fat or oil 油煎; 油炸: fried chicken 炸鸡 * bacon frying in the pan 在煎锅里煎着的腌肉. =>Usage at cook 用法见cook.
(idm 习语) have bigger/other fish to fry => fish1.
# `frying-pan (US `fry-pan) n
1 flat shallow pan with a long handle, used for frying food 长柄平底浅锅（煎锅）. =>illus at pan 见pan插图.
2 (idm 习语) out of the `frying-pan into the `fire from a bad situation to one that is worse 跳出油锅又入火坑; 愈来愈糟; 每况愈下.
`fry-up n (Brit) (dish of) fried food, esp bacon, eggs, sausages, etc 油煎食品（菜肴）（尤指腌肉、 蛋、 香肠等）: We always have a fry-up for Saturday lunch. 我们星期六的午饭总有一道油煎菜. fry 2
/ fra?; fra?/ n [pl v]
young or newly hatched fishes 小鱼; 鱼苗.
(idm 习语) `small fry => small.
NOTE ON USAGE 用法: When cooking we generally use 1 boiling water (in a saucepan) or 2 boiling fat/oil (in a frying-pan) or 3 dry heat (in an oven or under a grill). 使用cook一词时, 一般是指用（1）沸水（置於深锅中）或（2）热的动[植]物油（置於煎锅中）或（3）直接加热（置於烤炉中或烤架上）.
1 We boil vegetables, eggs, rice, etc by covering them with water and heating it. 将蔬菜、 鸡蛋、 大米等浸於水中煮叫boil. *We steam fish, puddings, etc by placing the food above boiling water. 将鱼、 布丁等置於沸水上蒸叫steam. *
2 Meat, fish, vegetables, etc can be fried in shallow oil or fat. 将肉、 鱼、 蔬菜等放在少许植物油或动物油里煎叫fry. *Chips, chicken pieces, etc can be completely covered by oil and deep-fried. 将土豆条、 鸡块等完全浸入油中炸叫deep-fry. *We saute vegetables very quickly in a small amount of oil. 用少量油将蔬菜很快一炒叫saute. *
3 We roast large pieces of meat, potatoes, etc and we bake bread, cakes, etc in the oven. 在烤箱里烘烤大块的肉、 土豆等叫roast, 烘烤面包、 糕饼等叫bake. *Small or flat pieces of meat, fish, etc are grilled (US broiled) by being placed under direct heat. 将小块的或切成片的肉、 鱼等置於发热器下面烘烤叫grill（美式英语叫broil）. *Boil, fry, roast and bake can be used in two types of sentence *boil、 fry、 roast、 bake可用於以下两种句型: We boil potatoes and The potatoes are boiling. Steam, saute and grill are generally only used in the first pattern. *steam、 saute、 grill一般只用於以上第一种句型. With boil we often use the container to refer to its contents 用boil时常以容器借代其所盛之物: The kettle's boiling. 壼开了.