American English

Definition of main adjective from the Oxford Advanced American Dictionary



[only before noun]
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 being the largest or most important of its kind Be careful crossing the main road. the main course (= of a meal) Reception is in the main building. Poor housing and unemployment are the main problems. The main thing is to stay calm. Thesaurusmainmajor key central principal chief primeThese words all describe something that is the largest or most important of its kind.main [only before noun] largest or most important:Turn left onto the main road. The main thing is to remain calm.major [usually before noun] very large or important:He played a major role in setting up the system. Major is most often used after a with a singular noun, or no article with a plural noun. When it is used with the or my/your/his/her/our/their, it means “the largest or most important”:Our major concern here is combatting poverty.In this meaning it is only used to talk about ideas or worries that people have, not physical things, and it is also more formal than main:Turn left onto the major road. The major thing is to remain calm.key [usually before noun] most important; essential:He was a key figure in the campaign. Key is used most frequently in business and political contexts. It can be used to talk about ideas, or the part that someone plays in a situation, but not physical things. It is slightly more informal than major, especially when used after a noun and linking verb:Speed is key at this point.central (somewhat formal) most important:The central issue is that of widespread racism. Central is used in a similar way to key, but is more formal. It is most frequently used in the phrase something is central to something else.principal [only before noun] (somewhat formal) most important:The principal reason for this omission is a lack of time. Principal is mostly used for statements of fact about which there can be no argument. To state an opinion, or to try to persuade someone of the facts as you see them, it is more usual to use key or central:The key/central issue here is…chief [only before noun] (somewhat formal) most important:Malnutrition is the chief cause of preventable [only before noun] (somewhat formal) most important; to be considered first:My prime concern is to protect my property.Patterns a/the main/major/key/central/principal/chief/prime aim/concern a/the main/major/principal road/town/city the main/key thing is to… to be of major/key/central/prime >importance>
See the Oxford Advanced Learner's Dictionary entry: main