English Reference
noun · adjective

principal

n. · adj.
US /ˈpɹɪnsəpəɫ/ UK /pɹˈɪnsɪpəl/ prin·ci·pal UK spelling principals

  1. 01 C1 Advanced Technical Finance

    n.the original amount of money you borrow or invest, not including the interest.

    n.the capital sum of a loan or investment as distinguished from interest or profit.

    Simple

    If you pay off the principal quickly, you will owe less interest over time.

    In context

    The borrower requested a restructuring of the debt to allow for smaller monthly payments toward the principal while maintaining the current interest rate.

    Usage

    Usually functions as an uncountable noun in this context.

  2. 02 B2 Upper Intermediate Theatre

    n.the most important actor or dancer in a show.

    n.a person who takes a leading part in a play, opera, or ballet company.

    Simple

    She was promoted to principal dancer after her amazing performance in Swan Lake.

    In context

    The principals of the touring company were praised for their technical precision and emotional depth during the opening night of the festival.

  3. 03 C1 Advanced FormalTechnical Law

    n.a person who has the main responsibility in a business or a legal agreement.

    n.the person or party who has primary responsibility for an obligation or who authorises another to act as an agent.

    Simple

    The agent signed the contract on behalf of the principal.

    In context

    In a principal-agent relationship, the agent is legally bound to act in the best interests of the principal at all times.

  4. 04 B2 Upper Intermediate

    adj.the main or most important part of something.

    adj.first in order of importance; primary or main.

    Simple

    The principal reason for the meeting was to discuss the new budget.

    In context

    The principal challenge facing the engineering team was the integration of legacy software with the new cloud-based architecture.

    Usage

    Always placed before the noun it modifies.

Don't confuse

principal vs principle — Principal is an adjective meaning main or a noun for a leader, while principle is always a noun meaning a fundamental rule or belief.

Usage merit principal · principal aim · principal analysis

As U.S.–based space companies, with SpaceX principal among them, receive billions in taxpayer-funded contracts , their environmental effects both on and beyond Earth will grow.

Phys.org· 15 Aug 2026

As U.S.-based space companies, principal among them SpaceX, receive billions in taxpayer-funded contracts , their environmental effects both on and beyond Earth will grow.

The Conversation· 12 Aug 2026

From Middle English principal, from Old French principal, from Latin prīncipālis.

Etymology adapted from Wiktionary, available under CC BY-SA 4.0.

This entry
Origin Latin prīncipālis
Level B2 · Upper Intermediate
Frequency Common
Updated