"In every word and every understanding." "Here are particular forms of spiritual gifts, for it is said: 'To one is given the word of wisdom, to another the word of knowledge, by the same Spirit' (1 Cor 12:8)" (Theodoret).
By "word" one may understand the word of God, divine revelation, everything God was pleased to reveal in the Lord Jesus Christ and to communicate to men through the Apostles. All this word, he says, has been handed over to you. You have been enriched by it.
Then he adds, "and understanding." Not only has the word been handed over to you, but its meaning has been explained. You have been brought to understand it. You understand the whole divine economy of salvation fully and richly.
Thus the Apostle wanted to express this: the whole will of God has been spoken to you, and you have understood it. Both things are abundant. This is God's gift to you in Christ Jesus from God the Father. I thank Him for this on your behalf.
Or by "word" the Apostle means the gift of speech, not natural but gracious: the gift of setting forth divine teaching clearly, precisely, and convincingly.
His thought would then be this: you not only understand everything fully, but you also know how to express everything well.
Thus St. John Chrysostom says: "In every word, not external, but divine. There is understanding without speech, and there is understanding with speech. Many have understanding but not speech, such as the unlearned, who cannot clearly express what they hold in the mind.
But you, he says, are not such. You are able both to understand and to speak." So also all our interpreters.
Since the Corinthians' failings were also in the use of the gift of speech, it is very appropriate to suppose that the Apostle has this gift in mind here as well.
The gift of speech, or the proper presentation of Christian teaching in the Church, is a gift of high value. It is higher than understanding, for by understanding a man enriches only himself, but by speech he enriches others also.