In the sexagenary cycle, the stem-branch name for 2025 is Yisi, written 乙巳 and conventionally romanized yǐsì. It is the 42nd pairing in the 60-year cycle and is also translated as Yin Wood Snake.
The name combines the second heavenly stem, 乙 (yǐ), with the sixth earthly branch, 巳 (sì). The stems and branches advance in fixed order, so each pairing returns only once every 60 years. The same designation appeared in 1965 and will return in 2085.
“Yisi” is the unaccented form often used in English text; the fully marked Mandarin Pinyin is yǐsì. It should not be confused with Jiachen, the name for 2024, or Bingwu, the name for 2026. The zodiac animal comes from the earthly branch, while the element and yin-yang quality come chiefly from the heavenly stem.