Latin is the language that prevailed in the ancient Roman empire and subsequently the Roman Catholic Church. Since higher education was originally primarily the province of the clergy, knowledge of latin became a core part of the higher educational curriculum (and remained so until the mid-20th century). The Roman Catholic Church started to allow services to be conducted in the vernacular in the 1970s after Vactican II and another major user of latin, lawyers, have started to favor English over Latin in legal terminology. Latin remains the primary language used to identify species in biology.
The "Romance Languages" (e.g. Portugese, Spanish, Italian, Romanian and French) all trace their roots to Latin.