Sherlock Holmes claimed to be a master of deduction, but he could also have called himself an expert of illation. “Illation” comes from the Latin root “illat-,” meaning “brought in,” and the root comes comes from the verb “inferre,” meaning to “bring in, bring about.” In medieval Latin, “inferre” meant “deduce.” For someone looking for clues, we’ll be more clear: “Illation,” “inference,” and “deduction” are synonyms. They all refer to the process of drawing a conclusion based on evidence and reasoning.