A saint can be holy without being sacred, and the difference matters
Sacred and holy sound interchangeable, but in Christian usage they point at different things. Holiness usually belongs to people and relationships; sacredness attaches to objects, places and events. The word holy itself grew from a Germanic root meaning whole or healthy, while sacred comes from a Latin term for what is dedicated to the gods.
Something sacred is set apart for worship, deserves spiritual respect, or stirs awe in believers. Latin sacer described what had been consecrated or purified for the gods, and it traces back to a Proto-Indo-European root linked to ceremony and ritual. Holy descends from Proto-Germanic hailagaz, from around 500 BC, built on a word for uninjured, sound and complete. Some things carry both labels, such as the Bible.
Holy is the stronger word, implying an inner character rather than a designation. Thomas Aquinas described holiness as the virtue that turns all a person's acts toward God, distinct from religion, which covers the specific duties of worship. The vocabulary for moving things into the sacred realm is rich: hallow, sanctify and consecrate, with desecrate and deconsecrate as their undoing. The verb hallow survives in English mainly in the Lord's Prayer, while the noun lives on in Hallowtide as an old word for saint. Some churches hold formal deconsecration services before a building is demolished or sold.
In Exodus, priests descended from Aaron are made holy through washing, robing, anointing and offerings, and the altar becomes so charged that anything touching it is itself set apart and barred from ordinary use. One commentary on Leviticus pictures holiness as an effervescence of divine presence that spreads by contact. Rabbinic Judaism frames sanctifying God's name as acts of mercy and martyrdom, with sin counted as desecration.
Other traditions have their own terms. Islam speaks of tazkiah, alongside ideas such as purification of the heart; Sufis often ask that God sanctify a saint's secret. Buddhists consecrate images of the Buddha and bodhisattvas in rituals called Buddhabhiseka. Latter-day Saint teaching stresses consecration both in Christ's title as the Anointed One and in each believer's commitment to live wholeheartedly by his will.
Source: Sacredness
