Something that is infinitesimal is extremely small.
①Mineral substances present in infinitesimal amounts in the soil.
②There was an infinitesimal pause.
《科学美国人》一篇题为 In every bit of nothing, there is something 也出现了这个表达：
If you pitch in, you join in and help with an activity.
①The agency says international relief agencies also have pitched in.
②Cartoonists have pitched in with their favourites from their own and other hands.
③The entire company pitched in to help.