The Alphabet and Church Pronunciation
The alphabet you already know
Latin is written with the very letters you are reading now — because this alphabet is the Latin alphabet. Classical Latin used twenty-three letters (no J, U, or W: I did the work of J, and V the work of U). Church texts as printed today use the familiar full set, so a canon of the 1917 Code or a line of the Vulgate looks typographically ordinary. The work is not learning new letters; it is learning what the words do.
Ecclesiastical pronunciation
The Church reads Latin the Italian way. C before e or i sounds like ch (caelum, "heaven," is CHEH-loom); g before e or i is soft (regina, "queen," is reh-JEE-nah); gn sounds like ny (agnus, "lamb," is AH-nyoos); v is a true v; every vowel is pure — ah, eh, ee, oh, oo. Say excelsis as ek-CHEL-sees and you have the whole system in one word.
Your first words
Fiat lux — "let there be light" (Genesis 1:3 in Jerome's Vulgate): fiat is "let it be," the same word as "the fiat of a ruler." In principio erat Verbum — "in the beginning was the Word" (John 1:1): principio gives us "principle," Verbum gives us "verb," and the sentence is the Vulgate's rendering of the Greek you met in the Greek course. One alphabet, three shelves.
The law's terms of art
The Canon Shelf keeps certain Latin phrases untranslated because they are terms of art — precise legal instruments, not ordinary words. Latae sententiae ("of a sentence already passed"): a penalty incurred automatically by the act itself, no tribunal needed. Ipso facto: "by the fact itself." Sanatio in radice, "healing at the root": the retroactive validation of an invalid marriage. These lessons exist so those phrases become readable instead of ornamental.
Why it matters on this site
Latin is the language of the Vulgate the Lantern Direct argues with (the "firmament" of Genesis 1, the "tabernacle" of Exodus, the horns on Moses' face at Exodus 34:29 all entered English through it), and the language of canon law the Canon Shelf will carry. To read either shelf critically is, in the end, to read a little Latin.