Yoga (Nitya Yoga)योग
This Yoga is not a yoga pose — it's one of 27 fixed combinations of the Sun's and Moon's longitudes added together. Each of the 27 has its own name and character, cycling continuously through the month.
A handful of these 27 Yogas are considered toxic ("Visha Yoga") for a portion of their duration — Vyatipata and Vaidhriti are considered the most severe, followed by Parigha, Vishkambha, Atiganda, Shoola, Ganda, Vyaghata, and Vajra. If one of these is active and you see a "Visha Yoga" warning on the page, that's this Yoga limb specifically, not a general bad-day indicator.
Computed as (Sun's longitude + Moon's longitude) divided into 27 equal 13°20' segments — a purely mathematical combination, distinct from Tithi (which is Moon minus Sun) and Nakshatra (which is Moon's position alone).