Latrīa is a Latin term (from the Greek λατρεία, latreia) used in Eastern Orthodox and Roman Catholic theology to mean adoration, a reverence directed only to the Holy Trinity. Latria carries an emphasis on the internal form of worship, rather than external ceremonies.
Catholic teachings 
In Catholic teachings, latria also applies to the Eucharist and Eucharistic adoration. In the 16th century, the Council of Trent made specific affirmations of the presence of Christ in the Eucharist and the theological basis for Eucharistic adoration and stated:
"The only-begotten Son of God is to be adored in the Holy Sacrament of the Eucharist with the worship of "latria", including external worship.
Pope Paul VI's 1965 encyclical Mysterium Fidei: also affirmed this belief and in items 56 stated:"The Catholic Church has always displayed and still displays this latria that ought to be paid to the Sacrament of the Eucharist, both during Mass and outside of it."
Latria vs. Dulia and Hyperdulia 
Latria is sacrificial in character, and may be offered only to God. Catholics offer other degrees of reverence to the Blessed Virgin Mary and to the Saints; these non-sacrificial types of reverence are called hyperdulia and dulia, respectively. In English, dulia is also called veneration. Hyperdulia is essentially a heightened degree of dulia provided only to the Blessed Virgin.
This distinction, written about as early as Augustine of Hippo and St Jerome, was detailed more explicitly by Thomas Aquinas in his Summa Theologiae, A.D. 1270, II II, 84, 1: "Reverence is due to God on account of His Excellence, which is communicated to certain creatures not in equal measure, but according to a measure of proportion; and so the reverence which we pay to God, and which belongs to latria, differs from the reverence which we pay to certain excellent creatures; this belongs to dulia, and we shall speak of it further on (II II 103 3)"; in this next article St. Thomas Aquinas writes: "Wherefore dulia, which pays due service to a human lord, is a distinct virtue from latria, which pays due service to the Lordship of God. It is, moreover, a species of observance, because by observance we honor all those who excel in dignity, while dulia properly speaking is the reverence of servants for their master, dulia being the Greek for servitude."
Linguistic distinctions in English 
Generally, in English, the word adoration is reserved for God alone and therefore it aptly translates latria. The word worship is derived from the West Saxon dialect noun weorðscipe 'condition of being worthy', which is from weorð 'worthy' + -scipe '-ship'. The word worship is used in a strong sense in relation to God (latria), but also in a weak sense in relation to man: for instance, "His Worship the Mayor", or "Your Worship" (when addressing a magistrate in Court), or the worship of the saints (dulia) as distinct to the adoration of God (latria). Adoration provides a clear and unequivocal, and therefore better, translation of latria and expression of the absolute sacrificial reverence due to God alone.
"This worship called forth by God, and given exclusively to Him as God, is designated by the Greek name latreia (Latinized, latria), for which the best translation that our language affords is the word Adoration. Adoration is different from other acts of worship, such as supplication, confession of sin, etc., inasmuch as it formally consists in self-abasement before the Infinite, and in devout recognition of His transcendent excellence."
Roman Catholic and Eastern Orthodox Christians especially adore with latria during their religious service, the Mass or Divine Liturgy. Protestant Christians do not have a Eucharistic sacrifice per se; while Catholics consider themselves to literally participate in the sacrifice at the foot of Calvary, that what Christ offered once "participates in the divine eternity" (CCC § 1085).
- Catholic beliefs and traditions by John F. O'Grady 2002 ISBN 0-8091-4047-0 page 145
- The History of Eucharistic Adoration by John A Hardon 2003 ISBN 0-9648448-9-3 pages 4-10
- Vatican website: Mysterium Fidei item 56
- Mark Miravalle, S.T.D, What is Devotion to Mary?
- Harper, Douglas. "worship". Online Etymology Dictionary.
|Wikisource has the text of the 1913 Catholic Encyclopedia article Latria.|
- City of God, Chapter X St. Augustine (A.D. 354-430) on latria