投とう函かんとうかんCommon wordFreq.FrequencyTop 50,000ConjugationMeanings1noun, noun or participle which takes 'suru', transitive verbmailing; postingRefers to putting a letter or postcard into a mailbox or postbox. Commonly used as a suru-verb.手て紙がみをポストに投とう函かんした。I mailed the letter.投とう函かんする前まえに切きっ手てを貼はって