Adjective / Noun A2 — Elementary /meɪn/

Main — Definition, Examples & Usage

The most important thing — or the great pipe beneath your street.

Quick Definition

Main (adjective) — most important; chief: the main entrance, the main reason.

Main (noun) — a principal pipe or cable carrying water, gas, or electricity underground; also (literary/nautical) the open sea: the water main burst overnight; sailing the Spanish Main.

What Does Main Mean?

Main is one of the most frequent adjectives in English, ranked among the top 200 words in the British National Corpus. It describes whatever is most important, largest, or central in a group: the main road through a town, the main character in a novel, the main course of a meal. Because it is so common, learning to use it naturally — and knowing when to prefer major, chief, or principal — is a key step for any learner beyond A2 level.

As a noun, main appears in everyday British English in compounds such as water main, gas main, and the plural the mains (the domestic supply of gas, water, or electricity). The literary noun sense — the open sea — survives in fixed phrases such as the Spanish Main and the old expression with might and main (with all one's strength).

Etymologically, main traces to Old English mægen (power, strength), related to Old Norse meginn. The sense shifted from "strong, mighty" to "principal" during the Middle English period, around the 13th–14th centuries. This same root underlies the archaic phrase by main force (by sheer physical strength).

Example Sentences (A2 → C1)

SentenceLevel & usage note
The main door of the school is always open. A2 — adjective before a concrete noun
The main purpose of the exercise is to improve reading speed. B1 — adjective modifying an abstract noun
One of the main advantages of living in the city is public transport. B1 — one of the main + plural noun (common in essays)
The government's main concern remains the rising cost of living. B2 — formal register; adjective in subject complement position
In the main, the committee welcomed the proposed reforms, though several members expressed reservations about the timetable. C1 — adverbial idiom in the main (= mostly, on the whole)

Collocations

CollocationExample
main roadTurn left at the main road and continue for half a mile.
main courseFor the main course, I ordered grilled salmon.
main entrancePlease use the main entrance on Bridge Street.
main characterThe main character is a young detective from Manchester.
main reasonThe main reason for the delay was bad weather.
main idea / main pointSummarise the main idea of each paragraph in one sentence.
main office / headquartersOur main office is located in Edinburgh.
main clauseIdentify the main clause in each compound sentence.
water mainEngineers worked through the night to repair the burst water main.
in the mainIn the main, the feedback was positive.

Usage Notes

Main vs Major vs Chief vs Principal

Main is the most neutral and everyday word for "most important". It usually appears directly before a noun: the main problem, the main street.

Major emphasises scale or significance, and is especially common with problems, changes, and events: a major accident, a major breakthrough. You would not normally say the major course (for the main course of a meal).

Chief is formal and often describes the single most prominent person or reason: the chief executive, the chief concern. It can also follow a noun as in editor-in-chief.

Principal is academic and formal. It is preferred in financial or legal contexts (principal and interest) and in education (the principal of a school). In writing, it is close in meaning to main but slightly more elevated in register.

Common Mistakes

Watch Out For

The mane issue is the lack of funding.

The main issue is the lack of funding. (mane = the hair on a lion's neck; do not confuse the spelling)

One of the main advantage is lower cost.

One of the main advantages is lower cost. (after one of the main, always use a plural noun)

The mainly problem is communication.

The main problem is communication. (mainly is an adverb, not an adjective; use main before a noun)

Related Words

mainly (adverb) mainland mainstream mainstay mainframe major chief principal primary central

Synonyms

chief principal primary major central foremost predominant leading

Antonyms

minor secondary subsidiary peripheral trivial

Practise This Word

Flash Cards Complete the Sentence Vocabulary Quiz Hangman

Frequently Asked Questions about “main”

What does main mean in English?
As an adjective, main means most important or chief: 'the main entrance', 'the main reason'. As a noun, main refers to a large pipe or cable — for example, 'a water main' — or, in literary contexts, to the open sea: 'sailing the Spanish Main'.
Is main an adjective or a noun?
Main is most commonly used as an adjective meaning chief or principal: 'the main idea'. It can also be a noun, especially in the phrase 'water main' (a large underground water pipe) or in the literary expression 'the main' (the open sea). Both uses are standard British English.
What is the difference between main and major?
Both main and major mean chief or most important, but they are used in slightly different contexts. Main often describes a single most-important thing (the main course, the main road), while major tends to emphasise scale or significance (a major problem, a major city). In many contexts they are interchangeable, but main feels more neutral and everyday.
What is a main clause in English grammar?
A main clause (also called an independent clause) is a clause that can stand alone as a complete sentence because it contains a subject and a verb and expresses a complete thought. For example, in 'She left early because she was tired', 'She left early' is the main clause and 'because she was tired' is the subordinate clause.
What does 'in the main' mean?
The phrase 'in the main' is a formal idiom meaning 'mostly' or 'on the whole'. Example: 'The feedback was, in the main, very positive.' It is slightly old-fashioned but still appears in written and formal British English. A more common alternative is 'on the whole' or 'mostly'.
What is a water main?
A water main is a large underground pipe that carries the public water supply. In British English, 'the mains' (usually plural) refers to the public supply of water, electricity, or gas connected to a building: 'The house is connected to the mains.' You might also hear 'mains water', 'mains electricity', or 'mains gas'.
What are common collocations with main?
Common collocations with main as an adjective include: main road, main course, main entrance, main reason, main idea, main character, main point, main goal, main office, and main clause. As a noun: water main, gas main, mains supply, mains electricity. Learning these collocations helps you sound natural in both spoken and written English.
How is main different from mainly?
Main is an adjective (it modifies a noun): 'the main problem'. Mainly is an adverb (it modifies a verb, adjective, or whole sentence): 'The delay was mainly caused by traffic.' A common learner error is using mainly before a noun — 'the mainly problem' — which is incorrect. Always use main before a noun.
What is the etymology of the word main?
The adjective main comes from Old English 'mægen' meaning strength or power, related to Old Norse 'meginn' (strong). By the Middle English period it had shifted to mean chief or principal. The noun sense (open sea) derives from the same root via the idea of the 'great' or 'mighty' sea. The word entered common usage around the 13th–14th centuries.
How can I practise the word main in English?
Try LexFizz's Complete the Sentence exercise to practise main in context — distinguishing it from major, chief, and principal is a common exam task. The Flash Cards tool also covers high-frequency adjectives. Reading news articles is a great source of natural collocations such as 'main road', 'main concern', and 'main character'.