noun
one grain; one drop; one bead
Counts a single small roundish object such as a grain of rice, a drop of liquid, a bead, or a pill. The reading ひとつぶ is the everyday form; いちりゅう is a rare Sino-Japanese reading used in some fixed contexts.
お米を一粒も残さず食べた。
I ate every single grain of rice.
この薬は一粒でよく効く。
This medicine works well with just one pill.
Compound of 一 (ひと, 'one') and 粒 (つぶ, 'grain, drop'). The reading ひとつぶ is the native Japanese combination; いちりゅう is the Sino-Japanese reading, rarely used.