This guide covers the three overlapping federal systems that govern leave and workplace accommodation, and the state and contractual layers that sit on top of them. Part 1 sets out federal leave law end to end: coverage, eligibility, qualifying reasons, the twelve-month measuring method, intermittent leave, certification and recertification, notice obligations on both sides, restoration, and the key employee exception. Part 2 covers disability accommodation: the definition of disability, qualified individual and essential functions, the interactive process, categories of accommodation, undue hardship, direct threat, medical inquiries, and confidentiality. Part 3 covers pregnancy, childbirth, and lactation. Part 4 covers military leave and genetic information. Part 5 addresses how the systems interact, including concurrent designation, benefit continuation, workers compensation overlap, and the exhaustion trap. Part 6 covers enforcement, deadlines, damages, and the employer policies that prevent most disputes.