Today's introit is taken from Psalm 65.
Omnis terra adoret Te, Deus, et psallat Tibi: psalmum dicat nomini tuo, Altissime. * Jubilate Deo, omnis terra, psalmum dicite nomini ejus: date gloriam laudi ejus.
Let all the earth adore Thee, O God, and sing to Thee: let it sing a psalm to Thy name, O most High. * Shout with joy to God, all the earth, sing ye a psalm to His name: give glory to His praise.
Omnis - all. Agrees with terra, which it modifies.
terra - land or earth. Subject of the verb adoret.
adoret - may it adore. The verb is adoro/adorare/adoravi/adoratum. This is the subjunctive, indicating wish or desire.
Te - Thee/you. Accusative case, since it is the direct object of the verb adoret.
Deus - O God. Vocative case, since God is being addressed.
et - and
psallat - may it sing. Subjunctive of the verb psallo/psallere which means to psalm or to sing with the harp.
Tibi - to Thee. Dative case.
psalmum - a psalm. Accusative case, as direct object of the verb dicat.
dicat - May it say. Subjunctive of the verb dico/dicere/dixi/dictum - to say. The subject of the verb is still terra.
nomini - to the name. Dative of nomen - name.
tuo - Thy/your. Dative to agree with nomini, which it modifies.
Altissime - O most high. Vocative case since it is an address. Altus is high. Altissimus is the superlative form - indicating most high or very high or highest. See grammatical note below.
Jubilate - Rejoice (plural form). Imperative form of the verb jubilo/jubilare/jubilavi/jubilatum, indicating a direct command.
Deo - to God. Dative case of Deus.
omnis - all. Modifies terra.
terra - land or earth. Vocative case.
psalmum - a psalm. As before.
dicite- say (plural). Imperative form of the verb dico. In the previous sentence dicat was used; here there is a direct command.
nomini - to the name. As above.
ejus - his or of him.
date - give (plural). Imperative of the verb do/dare/dedi/datum - I give.
gloriam - glory. Accusative case as direct object of the verb date.
laudi - to the praise. Dative case of laus/laudis - praise.
ejus - his.
Grammatical Note - Comparison of Adjectives.
There was an example of a superlative form in this introit - altissimus, meaning most high or very high.
Comparison of adjectives has three forms - standard, comparative, and superlative.
Altus - high
Altior - higher or quite high.
Altissimus - highest or very high.
The endings -ior and -issimus are characteristic of the comparative and superlative forms, though these do decline (change slightly their endings) like other adjectives, depending on the gender, number and case of the noun that is being modified. So in the introit, we actually have Altissime, since it is vocative case - O most high.
Some adjectives don't compare regularly. A good example is bonus - good.
Bonus - good
Melior - better or quite good.
Optimus - Best or very good.