This hymn may be sung every night of the year. There are four strophes. Here is the first.
|Te lucis ante terminum
rerum creátor, póscimus,
ut sólita cleméntia
sis præsul ad custódiam.
|Before the light’s end, we ask you,
the Creator of [all] things,
to be our protector at the watch,
according to your usual mercy.
For the melody, cf. the following video. There are a variety of settings for the various seasons of the liturgical year. Also, you will notice that the lyrics in the video are different from those translated here. For our purposes we are using the Liturgy of the Hours, while the Roman Breviary has a slightly different wording. Either version may be sung to the same melody.
Since we are dealing with poetry, it is difficilior, more difficult to read than ordinary writing. First, see what these lines of text look like when rearranged into an English word order (subject – verb – object):
Ante terminum lucis, [nos] poscimus te, creator rerum, ut sis praesul ad custodiam, solita clementia.
Ante terminum lucis = before the end of light, which is to say before sunset. The terminum is the end or boundary of a thing. lucis is from lux, lucis, light. Jesus said in Jn 12:36, “Dum lucem habetis, credite in lucem, ut filii lucis sitis” / “While you have the light, believe in the light, that you may be sons of the light.” In the hymn under consideration, the word lucis precedes terminum. It is very common in Latin that a genitive precedes that which it is “of”, as in the title of the Dogmatic Constitution on Divine Revelation, Dei Verbum. In English the reverse is usually the case: We say the Word of God, or the end of the light, rather than the of God Word, or the of the light end.
[nos] poscimus te = we ask you. We is implied in the plural, first-person form of poscimus.
creator rerum = Creator of things, maker of things. A res is a thing. Rerum is genitive plural. We address God who has made things. We consider that all of creation is made by the rerum creator.
praesul = protector. Thus, ut sis praesul ad custodiam = that you will be the protector on guard duty.
solita clementia = by your usual clemency, by your accustomed mercy.