Mormon usage of the term is in line with one of the common New Testament meanings. According to 2 Peter 3:2, the work of the apostles was to convey the teachings of the prophets and of Jesus to the Church. Jude understands the apostles themselves also to be prophets, those who speak the words of Jesus Christ. But perhaps the definition in Acts 1:21-22, as someone who was with Christ throughout his ministry, is the most relevant for Latter-day Saints.
Anyone with a smattering of knowledge about the New Testament knows that the English word apostle is derived from a Greek word meaning "messenger," specifically a special messenger or envoy. In the early Church the word was used in several ways. Indeed, the use of the word after Paul appears to have been more ambiguous than it was in the early Church (Anchor Bible Dictionary, s.v. apostle).
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