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“Principle” is a noun. It can be described as a rule or idea in relation to behaviour or how something works. “Principal”, on the other hand, can be either used as a noun or an adjective. As an adjective, it can be used to signify the first position in order of importance, or in relation to financial investment or lending. As a noun, it can be used to describe a person of the highest position in an organisation or group, or can also be used in relation to financial investment or lending. 

Because they are pronounced the same but have different meanings, we call these words homophones. These words are often confused – even by native English speakers. So, how to tell the difference between them? In this IELTS Grammar 101, we’ll give you some tips on telling them apart. 

  • Difference between principle and principal 

  • Synonyms of principle and principal 

  • Use principle and principal in a sentence 

Principle or principal: the definitions


Is a noun: A word that refers to a person, place, thing, event, substance, or quality. 


Can be either – 

An adjective: A word that describes a person, place, thing, event, substance or quality. 

A noun: A word that refers to a person, place, thing, event, substance, or quality.

Principle or principal: the difference


  • A rule or truth about what is right or how you should behave 


  • Adjective: The main, primary or first, in order of importance 

  • Adjective: The original sum invested or lent 

  • Noun: The person of utmost position or importance in an organisation or group 

  • Noun: The sum of money that has been invested or lent, on which interest is paid. 

Principle or principal: the synonyms


Could also mean (synonyms): basis, doctrine, foundation, fundamental, proposition, truth. 


Synonyms include: dominant, key, leading, main, paramount, primary, prominent, administrator, boss, chief, director, CEO, capital sum, capital, working capital. 

Principle or Principal: in a sentence


  • The workplace must uphold the principles of Fair Work Australia. 

  • My father was a man of principle. 

  • We each have our own moral principles. 

  • The principles of Newtonian physics. 

  • My friend would always pay back money borrowed, as a matter of principle. 


  • It was my principal reason for quitting my job. 

  • The principal at my school is very kind. 

  • The principal and interest must both be paid. 

  • She was made principal of that international bank.

Want to learn more about commonly confused words?

In written English, it is important to know the correct spelling of a word you want to use. You don’t want to write “weak” when you mean “week” even though they sound the same. In spoken English, spelling is less important, but pronunciation is. Think about the word “lead” which can be pronounced as “led” or “leed.” Because these words cause a lot of confusion, it’s well worth to spend a few minutes to know the difference: homophones vs homographs vs homonyms. Read more here

People often use elude when they mean allude, or write allude when they should really write elude. There are other commonly confused words too: Do you know the difference between belief or believe? That is the question of another article where we explain the difference between these two commonly misused words. Read it here.