Panchanga · पक्षः
Paksha — The Lunar Fortnight
पक्ष (pakṣa) literally means "side" or "wing" — each lunar month has two sides, or fortnights, of 15 Tithis each.
Shukla Paksha — शुक्ल पक्ष
The bright, waxing fortnight — from Amavasya (new moon) to Purnima (full moon), as moonlight grows each night. Shukla (शुक्ल) means "white" or "bright."
Krishna Paksha — कृष्ण पक्ष
The dark, waning fortnight — from Purnima back to Amavasya, as moonlight shrinks each night. Krishna (कृष्ण) means "dark" or "black" here (unrelated to the deity Krishna, though the same word).
Why it matters
Almost every festival date specifies its Paksha alongside its Tithi — for instance, Janmashtami falls on Ashtami (8th Tithi) of Krishna Paksha in Bhadrapada. Without the Paksha, a Tithi number alone is ambiguous, since both fortnights have a "Chaturthi" or an "Ashtami."
Related pages
See all 30 Tithi names across both Paksha, or the full Panchanga overview.