This paper argues that four keywords central to the founding of the United States—slavery, freedom, race, and equality—did not begin with fixed, modern meanings. Instead, in the early modern period they were fluid and often overlapping terms whose senses depended on context. Over the course of the eighteenth century, as America moved from an “aristocratic” to a “democratic” language, these words narrowed, hardened, and became mutually defining, eventually forming a tightly bound “semantic field”—similar to how “man/woman” and “husband/wife” define each other. By the era of the Revolution and early republic, slavery had narrowed to mean Black chattel bondage, race had acquired its modern sense of biological human categories (largely through Jefferson), and freedom and equality had become linked as near-synonyms opposed to slavery and race. The result was a stable, emotionally powerful linguistic structure that still shapes American thought about liberty and inequality today.