Vatican II demanded that we keep Latin in the Roman Rite as it is the language of the Church.

The three main places we do this is after the preface, after the peace and after the blessing.

After the preface we sing: sanctus sanctus sanctus dominus deus sabaoth, pleni sunt coeli et terra gloria tua hosanna in excelsis. Benedictus qui venit in nomine domini hosanna in excelsis. Which means literally: holy holy holy Lord God of Hosts, full they are heaven and earth of your glory, hosanna in the highest. Blessed is he who comes in the name of the Lord hosanna in the highest.

You can see with just a little word order change how we got our English translation which is in our missal today.

After the peace we sing: Agnus Dei qui tollis peccata mundi miserere nobis. Agnus Dei qui tollis peccata mundi miserere nobis. Agnus Dei qui tollis peccata mundi dona nobis pacem. Which means: Lamb of God, you take away the sins of the world: have mercy on us. Lamb of God, you take away the sins of the world: have mercy on us. Lamb of God, you take away the sins of the world: grant us peace.

After the blessing the Priest sings: Ite Missa Est (Go it is the dismissal). We respond: Deo Gratias (Thanks be to God).

These have been sung in Latin in our liturgy for over 1500 years. Let us not lose these treasures, which are easily understood in English, and let us keep just this little bit of Latin in our liturgies, as we keep the Greek Kyrie, to show our unity with the Church of all ages.