The morning star, used in describing typical whiteness (odātā, odātavaṇṇā, etc.) (D.ii.111), and also great brightness and purity (parisuddha-osadhātārakā viya) (It.20; MA.ii.638, 772; also Vism.ii.412).

Buddhaghosa says (MA.ii.714) that it is so called because, when it appears in the sky, people gather medicines and drink them by its sign. (Sukkā tārakā tassā udayato patthāya tena saññānena osadhāni ganhanti pi pivanti pi: tasmā Osadhī tārakā ti vuccati.)

The Itivuttaka Commentary (ItA.72) gives another explanation: that it contains bright rays of light, and that it gives efficacy to various medicines (ussannā pabhā etāya dhīyati osadhīnaṃ vā anubalappadāyikattā osadhī).

It is also used in similes to typify constancy, like the star Osadhī, which, in all seasons, keeps to the same path and never deviates there from (sabbautusu attano gamanavīthiṃ vijahitvā aññāya vīthiyā na gacchati sakavīthiyā va gacchati). (BuA.89)