“Pakkhi tithi” ka arth hai vah vishesh tithi jo har paksha (15 din ka chaandramaas ka ardha—Shukla paksha aur Krishna paksha) mein aati hai, aur jin par shravak–shravika vishesh sādhanā karte hain—jaise samayik, poshadh/paushadh, pratikraman, upvās, dān-śravak dharmādin.

• Shvetāmbara paramparā meṅ “Pakkhi” rogya tithiyān prāyam do hoti hain: Ashtamī (8) aur Chaturdaśī (14) – donoṅ Shukla aur Krishna paksha meṅ. In par poshadh, upvās, niyamit samayik karne ki prerna di jātī hai.
• Digambara paramparā meṅ ise “Pakṣaika Upavāsa” (har paksha meṅ ek upvās) ke rūp meṅ mānā jātā hai. Din vyakti apnī śakti aur niyam ke anusar chun sakta hai; anek parivāroṅ meṅ yah bhī Ashtamī/Chaturdaśī par hī rakhā jātā hai.

Saral bhāṣā meṅ: har paksha meṅ jo niyamit sādhana/vrat karne ke din niśchit kiye gaye hain, ve “Pakkhi tithi” kahāte hain—zyādatar 8vīṅ aur 14vīṅ tithi.