t one of those words is that which
those who speak that language use principally and more commonly to
signify that particular thing: and this is the word which should be
used for the sacramental signification. So also among sensible
things, that one is used for the sacramental signification which is
most commonly employed for the action by which the sacramental effect
is signified: thus water is most commonly used by men for bodily
cleansing, by which the spiritual cleansing is signified: and
therefore water is employed as the matter of baptism.

Reply Obj. 3: If he who corrupts the pronunciation of the sacramental
words--does so on purpose, he does not seem to intend to do what the
Church intends: and thus the sacrament seems to be defective. But if
he do this through error or a slip of the tongue, and if he so far
mispronounce the words as to deprive them of sense, the sacrament
seems to be defective. This would be the case especially if the
mispronunciation be in the beginning of a word, for instance, if one
were to say "in nomine matris" instead of "in nomine Patris." If,
however, the sense of the words be not entirely lost by this
mispronunciation, the sacrament is complete. This would be the case
principally if the end of a word be mispronounced; for instance, if
one were to say "patrias et filias." For although the words thus
mispronounced have no appointed meaning, yet we allow them an
accommodated meaning corresponding to the usual forms of speech. And
so, although the sensible sound is changed, yet the sense remains the
same.

What has been said about the various mispronunciations of words,
either at the beginning or at the end, holds forasmuch as with us a
change at the beginning of a word changes the meaning, whereas a
change at the end generally speaking does not effect such a change:
whereas with the Greeks the sense is changed also in the beginning of
words in the conjugation of verbs.

Nevertheless the princip[al] point to observe is the extent of the
corruption entailed by mispronunciation: for in either case it may be
so little that it does not alter the sense of the words; or so great
that it destroys it. But it is easier for the one to happen on the
part of the beginning of the words, and the other at the end.
_______________________

EIGHTH ARTICLE [III, Q. 60, Art. 8]

Whether It Is Lawful to Add Anything to the Words in Which the
Sacramental Form Consists?

Objection 1: It seems that it i