A Catholic–Orthodox–Protestant Glossary for the Confused (and Curious) Christian

As a cradle Catholic who converted to being a Protestant more than 20 years ago, and who is now Catholic-curious again — attending Mass for the past three months — I’ve found myself diving deep into topics that never sat well with me before and even contributed to my conversion out of Catholicism in the first place.

But something surprised me when I returned to Mass as an adult:

I don’t actually remember most of Catholic terminology from childhood.

Words are being used that feel vaguely familiar, yet completely foreign. Meanwhile, I’ve spent over two decades in various Protestant churches — each with their own vocabulary. And the Orthodox tradition adds another entirely different set of terms I had only heard from a distance.

So lately I’ve found myself confused — not doctrinally, but linguistically.

So many Christians believe the same core truths, but we speak different “Christian dialects.”

I’m sure I’m not alone.

So I put together this glossary-style guide to show how Catholic, Orthodox, and Protestant traditions often use different words for the exact same topics — or use the same words with slightly different meanings behind them.

My hope is to build clarity, charity, and unity — because a lot of confusion is simply vocabulary, not theology.

Below is a guide to key theological terms across Catholic, Orthodox, and Protestant traditions, with the Scriptures each tradition uses as its foundation — including verses from the Deuterocanonical and Orthodox Old Testament books.

SECTION 1: PEOPLE & PLACES

1. Priest vs. Pastor vs. Elder

Who leads the local church?

Catholic:

• Priest under a bishop

• Acts in persona Christi during sacraments (Luke 22:19)

• Celebrates the Eucharist and shepherds the parish

Orthodox:

• Priest under a bishop

• Spiritual father, steward of the mysteries (Malachi 2:7)

Protestant:

• Pastor, minister, or elder

• Leads by preaching, teaching, and pastoral care

• All believers are a “royal priesthood” (1 Peter 2:9)

“For the lips of a priest should guard knowledge…” — Malachi 2:7

2. Parish vs. Church vs. Congregation

What do we call the local community of believers?

Catholic:

• Parish

• Local community under a priest within a diocese (Titus 1:5)

Orthodox:

• Parish or temple/community under a bishop

• A “household of God” (1 Tim. 3:15)

Protestant:

• Church, congregation, or fellowship

• Gathering for worship and mutual encouragement (Heb. 10:24–25)

3. Diocese vs. Eparchy vs. District/Synod

How are churches organized regionally?

Catholic:

• Diocese — group of parishes under a bishop

Orthodox:

• Eparchy — same structure under a bishop

Protestant:

• District, conference, synod, etc.

• Organizational oversight and support (Acts 20:28)

SECTION 2: GATHERINGS & WORSHIP

4. Mass vs. Divine Liturgy vs. Worship Service

The main weekly gathering.

Catholic — Mass

• Sacrificial memorial of Christ’s death/resurrection (1 Cor. 11:26)

Orthodox — Divine Liturgy

• Mystical union of heaven and earth (Heb. 12:22–24)

Protestant — Worship Service / Sunday Service

• Focus on Scripture, preaching, prayer, praise (Col. 3:16)

5. Liturgy

Structured pattern of worship.

Catholic:

• The Church’s official worship — especially the Mass (Acts 2:42–47)

Orthodox:

• The Divine Liturgy is the heart of worship (Rev. 4:8–11)

Protestant:

• Varies from formal liturgies to spontaneous services (John 4:24)

6. Homily vs. Sermon

The teaching portion of the service.

Catholic — Homily

• Short reflection on readings (Neh. 8:8; Luke 4:16–21)

Orthodox — Homily / Sermon

• After Gospel reading; draws on Scripture and Fathers (Acts 17:2–3)

Protestant — Sermon

• Expositional or doctrinal teaching (2 Tim. 4:2)

Simple:

• Homily = shorter, tied to liturgy

• Sermon = longer, doctrinal exposition

7. Liturgical Calendar (Advent, Lent, etc.)

Structuring the year around Christ.

Each tradition observes seasons differently, but all use time to remember Christ’s life, death, and resurrection.

SECTION 3: SACRED ACTIONS — Different Words, Sometimes Different Theologies

8. Sacraments vs. Mysteries vs. Ordinances

Sacred acts Jesus gave the Church.

Catholic — Seven Sacraments

• Signs that truly convey grace (Matt. 28:19; John 6:53)

Orthodox — Holy Mysteries

• Same seven, emphasizing divine mystery (1 Cor. 4:1)

Protestant — Two Ordinances

• Baptism & Communion as symbolic obedience (1 Cor. 11:26)

Shared: All honor Baptism and Communion.

9. Eucharist vs. Communion vs. Lord’s Supper

The meal Jesus instituted.

Catholic — Eucharist

• Real Presence through transubstantiation (John 6:53–56)

Orthodox — Holy Eucharist

• Real Presence via the Spirit (epiclesis)

Protestant — Communion / Lord’s Supper

• Varies from real presence to symbolic memorial

10. Confession / Reconciliation vs. Confessing to God Directly

Catholic — Sacrament of Reconciliation

• Confess to priest; absolution (John 20:22–23)

Orthodox — Confession

• Before priest as spiritual physician (Psalm 32:5)

Protestant — Confession to God

• Direct repentance (1 John 1:9)

11. Baptism

Catholic:

• Removes original sin; entry into Church (John 3:5)

Orthodox:

• Triple immersion; immediate full initiation (Rom. 6:3–4)

Protestant:

• Outward sign of inward faith; infant vs. believer baptism varies depending on denomination

12. Confirmation vs. Chrismation vs. Profession of Faith

Catholic — Confirmation

• Gifts of the Spirit through chrism and laying on of hands (Acts 8:14–17)

Orthodox — Chrismation

• Immediately after baptism (2 Cor. 1:21–22)

Protestant — Confirmation

• Public affirmation of faith (Rom. 10:9–10)

13. Anointing of the Sick vs. Healing Prayer

Catholic — Sacrament

• Spiritual and sometimes physical healing (James 5:14–15)

Orthodox — Holy Unction

• Healing of soul and body (Mark 6:13)

Protestant — Healing Prayer

• Faith-filled prayer; not sacramental

14. Holy Orders vs. Ordination

Catholic — Holy Orders (Sacrament)

• Deacon, priest, bishop (1 Tim. 4:14)

Orthodox — Holy Orders

• Similar; apostolic succession (Acts 6:6)

Protestant — Ordination

• Commissioning, not sacramental (Eph. 4:11–12)

SECTION 4: PRAYER & DEVOTION — Same Heart, Different Traditions

15. Saints

Catholic / Orthodox:

• Saints are the faithful departed; some canonized or glorified

• Intercession of saints (Wisdom 3:1; Rev. 5:8)

Protestant:

• All believers are saints (Eph. 1:1)

16. Intercession

Catholic / Orthodox:

• Saints and angels intercede (Tobit 12:12–15)

Protestant:

• Only living believers intercede (1 Tim. 2:5)

17. Veneration

Catholic / Orthodox:

• Honor (dulia) to saints; worship (latria) only to God (Luke 1:28, 48)

Protestant:

• Honor examples, not invocation (1 Tim. 2:5)

18. Relics

Catholic / Orthodox:

• Venerated as reminders of God’s work (2 Kings 13:21; Acts 19:11–12)

Protestant:

• Generally avoided due to concerns of idolatry (Ex. 20:4–5)

19. Rosary vs. Prayer Rope vs. No Beads

Catholic:

• Meditative prayer on Christ’s life through decades

Orthodox:

• Jesus Prayer with prayer rope

Protestant:

• Typically spontaneous prayer

20. Novena vs. Paraklesis / Akathist vs. Persistent Prayer

Catholic:

• Nine-day devotion (Acts 1:14; 2:1–4)

Orthodox:

• Multi-day services (Phil. 4:6)

Protestant:

• Persistent prayer emphasis (Luke 18:1–8)

21. Catechism

Different books, same purpose: teaching the faith.

Catholic — CCC

Orthodox — Catechetical homilies

Protestant — Heidelberg, Westminster, etc.

Why This Glossary Matters:

Different traditions often use different words for the same realities:

• Mass vs. Worship Service

• Priest vs. Pastor

• Eucharist vs. Communion

• Parish vs. Church

And sometimes we use the same word but mean slightly different things:

• Confession

• Baptism

• Saints

• Tradition

If we don’t understand the vocabulary, we assume we disagree — when in reality, many of us are simply speaking different Christian “dialects.”

“There is one body and one Spirit… one Lord, one faith, one baptism, one God and Father of all.” — Ephesians 4:4–6

Different vocabulary — one Redeemer.

Different expressions — one Gospel that saves.

Different traditions — one Body in Christ.

I feel like so many times, people within different traditions spend most of their time disagreeing with each other and picking each other apart and end up missing the whole point. While simultaneously pushing unbelievers away because our division is what they end up seeing, instead of the love of Christ.

I will add more glossary terms and I come across them, so check back often to see if it has been updated.