The Catechism in Questions & Answers

431. What is meant by the term “the ministry of the word”?

John 1: 1-14 describes the Son of God as the “Word” (Logos). All things were created by this “Word”.
The Apostle ministry shares in the “word” because the Lord (Logos) has also given this ministry the commission to teach. It is also in this sense that Acts 6: 4 is to be understood: “But we will give ourselves continually to prayer and to the ministry of the word.”

Logos: see Question 101.