The Catechism of the Summa II. OF GOD'S NATURE AND ATTRIBUTES (D)

(D)

When we speak of God, or endeavour to express our thought concerning Him, have the words we use a correct meaning? 

Most certainly: for these words, although used primarily to designate the perfections in a creature, can be transferred to designate what in God corresponds to these very perfections (XIII. 1-4).

When applied to God and to creatures, have these word the same meaning or one wholly different? 

When applied to God they have the same meaning but in a superlative degree, that is, when used to designate perfections in creatures in the fulness of their meaning they truly signify these perfections: whereas when use to designate the divine perfections, or whatever is attributed to God, if all that they tell is verily in God they do not tell fully the perfections they express in God (XIII. 5)

Then whatever we may tell of God, and however exalted be our expressions concerning Him, for us God ever remains unutterable?

Yes; but in this life we cannot do anything more salutary, more perfect, and more noble than speak of Him and of all that concerns Him even though our thoughts fall short of Him and our speech fail (XIII. 6-12).

Next  - III. OF THE DIVINE OPERATIONS

Pegues OP, R P Thomas. Catechism of the "Summa Theologica" of Saint Thomas Aquinas for the Use of the Faithful (pp. 26-27). Veritatis Splendor Publications. Kindle Edition.