Though in the late twentieth century the word "sacramentary" was used in the United States and other English-speaking countries for the English translation of the Roman Missal, a true sacramentary is not the same as a Missal. It contains more than a missal in terms of other services, and less in that texts and readings said by others during the Mass are not included.

It is the book for the priest celebrant, containing all and only the words spoken (or sung) by him, usually assuming the presence of a choir and deacon. At the time that these books were written it was not yet the custom for the celebrant to repeat at the altar whatever was sung by the ministers or the choir, as became the rule in the Tridentine Mass. Thus Sacramentaries contain none of those parts of the Mass, not only no Scripture readings, but also no Introits, Graduals, Offertories and so on, but only the Collects, Prefaces, Canon.

On the other hand sacramentaries provide the priest's texts at other occasions besides Mass. As they suppose that the celebrant is normally a bishop, they usually supply the texts for ordinations, at the consecration of a church and altar and many exorcisms, blessings, and consecrations that were later inserted in the Pontifical and Ritual.

A number of versions of the texts for Sacramentaries, chiefly of the Roman Rite, are still extant, either complete or in part. Of these textual groups the most important are the three known by the names Leonine, Gelasian, and Gregorian. Their date, authorship, place, and original purpose have been much discussed.

The name Sacramentarium is equivalent to the other form also used (for instance, in the Gelasian book), Liber Sacramentorum. The form is the same as that of the word Hymnarium, for a book of hymns. Gennadius of Massilia (fifth cent.) says of Paulinus of Nola: "Fecit et sacramentarium et hymnarium" (De viris illustribus, XLVIII). The word sacramentum or sacramenta in this case means the Mass. Sacramenta celebrare or facere is a common term for saying Mass.

Read more about Sacramentary:  Decline of The Sacramentary, Textual Groups