What is the definition of a sacrament?

The correct definition of a sacrament is "a holy ordinance instituted by Christ using sensible signs." This understanding captures the essence of what a sacrament is in Christian theology, particularly as articulated in the Westminster Shorter Catechism. Sacraments serve as outward and visible signs of inward and spiritual grace, meaning that they are tangible elements that signify a deeper spiritual reality.

This definition underscores that sacraments are not merely rituals or ceremonies; they are specifically instituted by Christ himself, such as baptism and the Lord's Supper, and they have a divine origin and purpose. By using sensible signs—things that can be seen and touched—they convey profound spiritual truths and effects.

The other options do not align with the theological understanding of sacraments. For instance, while rituals may have significance in church membership, the notion of a sacrament is broader and rooted in Christ's institution. An event occurring at church gatherings does not encompass the sacramental nature and intent. Finally, labeling sacraments as optional ceremonies undermines their essential role in the faith and practice of Christianity as instituted by Christ.