adj (1)(较)重(主)要的((more) important，or serious than others of the same type)[通常作attrib]：a～issue/factor/cause/role/discovery重要问题/因素/原因/角色/发现;a～illness/industry 重病/重工业;on a～military offensive 进行一次重要的军事进攻;The～export of the country is coffee.该国的主要出口商品是咖啡。a～poet/artist/play/novel 大诗人/大艺术家/重头戏/一部主要小说;Citrus fruits are a～source of vitamin C.柑橘是维生素C的主要来源。〖同〗leading，chief;〖反〗minor，secondary;

(2)较大(多)的(greater in size or amount;bigger)[通常作attrib]：a～river/road/repair/operation主河道/干道/大修/大手术;a～improvement in sb's work 某人工作的重大改进;the～portion of the liquid 液体的大部分;The～part of the work was undertaken.大部分工作已有人承担了。〖同〗greater，larger，main;〖反〗lesser，smaller;

(3)大(年长)的(first or older of two brothers or boys with the same surname(esp in the same school))(BrE)(joc)：Brown/Smith～大布朗/史密斯;

(4)(音乐)大调的((music)of key or scale)：a～interval/chord/scale/key大音程/大调三和弦/大音阶/大调;a sonata/concerto in C～，C大调奏鸣曲/C大调协奏曲;the F～symphony F大调交响乐;

n (1)主修课(指大学课程)(principal subject or course chosen at a college)[C](AmE)：History was his～.历史是他的主修科目。My～s were English and French.我主修的科目是英语和法语。

(2)(大学某专业的)主修学生(student specializing in a particular subject)[C](AmE)：a psychology/history/philosophy～主修心理学/历史/哲学的学生;Are most of you English～s? 你们多数是英语专业的学生吗?

vi 主修(specialize in a particular subject)[I+prep(in)](AmE)：～in math主修数学;She～s in Spanish. 她主修西班牙语。What did you～in at university? 你上大学时主修什么课程?