The word viaduct is a modern English formation from the mid-19th century, directly constructed from Latin elements to meet the need for a term describing the new, large-scale railway bridges. It combines via, meaning "road" or "way," with ductus, meaning "a leading" or "conduit," from the verb ducere, "to lead." The literal construction, "a leading of the way," perfectly captures the function of the structure: to lead a road or railway across an obstacle. While the Latin roots are ancient, the specific compound is a modern, logical neologism that transparently describes its engineering purpose.

Structure: via (way) + duct (lead) - via: Latin origin, meaning "way" or "road." In this word, it functions as a combining form indicating a path for travel. - duct: Latin origin, from the past participle stem of ducere, meaning "to lead." In this word, it functions as a root indicating something that carries or conducts.