latitudo

Latitudo, latitudinis is third declension feminine, one of a tidy family of abstract nouns built on adjectives with the suffix -tudo: latus gives latitudo, longus longitudo, altus altitudo, magnus magnitudo. All of them add -in- before the case endings and all of them are feminine, which is easy to forget when the nominative ends in -o.

The measurement sense is the everyday one, and Roman surveyors and geographers use it constantly alongside longitudo. The astronomical sense of latitude, distance from the equator, is a late technical development, so a classical latitudo is width and nothing more. Watch also latitudo verborum, "looseness of language", and remember that latus, "broad", and latus, "side", and latus, "carried", are three different words wearing the same coat.