Jupiter (Guru) — the teacher of the chart
Guru means both "teacher" and "heavy," and Jupiter is exactly that: the largest planet in the sky and the weightiest benefic in the chart. Classical Jyotish makes it the priest and counselor of the gods — the graha of wisdom, children, wealth, and the sense that life means something. Where Jupiter sits and what it aspects tends to grow, protect itself, and turn out better than the raw ingredients predicted. It spends about a year in each sign, so its transit sets the tone of whole seasons of a life. Jupiter's question is never whether more is possible, but whether more is wise.
As karaka — significator — Jupiter stands for wisdom, children, wealth and fortune, teachers and counsel, dharma (right purpose), and expansion. Its Vimshottari mahadasha runs 16 years: a whole season of life colored by this graha's agenda.
Jupiter rules Sagittarius and Pisces, is exalted in Cancer (deepest at 5°), and is debilitated in Capricorn (deepest at 5°) — exaltation is where a graha's nature works at its cleanest, debilitation where it has to work uphill. Jupiter counts the Sun, Moon, and Mars as natural friends; Saturn is neutral; Mercury and Venus are natural enemies.
Strong Jupiter is generosity with judgment: optimism that survives evidence, counsel people actually follow, luck that on inspection turns out to be accumulated goodwill. It gives teachers, mentors, and the rare wealth that makes everyone nearby slightly richer too.
Expansion without discernment bloats: overpromising, preaching, weight gained in body or ego, opportunities said yes to until none get real attention. An afflicted Jupiter believes its own advice too easily. Growth, it must relearn, includes pruning.
Teaching and academia, law and justice, finance and banking, counseling, ministry, publishing — the advisory professions, where wisdom is the product. Jupiter also marks mentors inside any field: the person juniors instinctively bring their dilemmas to.
Jupiter loves by encouraging — it wants partners and children alike to become bigger versions of themselves. Its lesson is to guide without grading: home is not a classroom, and love is not a syllabus.
BPHS names Guru the counselor of the gods, sattvic and brahmin in temperament; Phaladeepika assigns it children, wealth, and wisdom as chief karakatvas. Its mahadasha runs sixteen years.
Where in your life is Jupiter asking to be expressed more cleanly?