Ma'anar ƙamus na "aikin capillary" shine ikon ruwa don gudana a cikin kunkuntar wurare ba tare da taimakon, ko gaba da, ƙarfin waje kamar nauyi ba. Wannan yana faruwa ne saboda mannewa da haɗin kai na ruwa, da kuma tashin hankali na saman, wanda ke ba shi damar hawa sama ko a ja shi zuwa kunkuntar wurare, kamar ƙananan tubes ko capillaries da ke samuwa a cikin kayan da ba su da kyau kamar ƙasa, takarda, ko zane. Aiki na capillary yana taka muhimmiyar rawa a yawancin al'amuran halitta, irin su shan ruwa na shuka, kwararar jini a cikin dabbobi, da motsin ruwa ta hanyar kayan da ba su da tushe.