A greenfly is a very small green insect that lives on young plants and sucks juice from the new growth. Gardeners in Britain use this word a lot; in American English people more often say aphid. Though actually, it is not a fly in the everyday sense — it does not buzz around your food like a housefly. It is soft-bodied, tiny, and it sits in groups on stems and on the underside of leaves. One greenfly does little harm; a crowd can ruin a rose or a young vegetable plant, leaving leaves curled and sticky. The word is ordinary garden talk, not a scientist's Latin name. You may also hear greenfly for the same insects when they are not perfectly green, because the garden name stuck.

蚜蟲（英國說法；不是會飛來飛去的蒼蠅）