cardinal

Compared meaning: very important, of great significance (adjective).

比较义项：主要的，重要的（形容词）。

• cardinal 本词

  Very formal and now mostly limited to fixed phrases such as 'cardinal sin', 'cardinal rule' or 'cardinal virtue'; rarely used freely to modify other nouns.

  语气非常正式，如今多局限于固定搭配，如“cardinal sin”“cardinal rule”“cardinal virtue”，很少自由地修饰其他名词。

  Missing a deadline is considered a cardinal sin in this profession.

  在这个行业里，错过截止日期被认为是一项不可饶恕的大忌。

• primary

  Emphasizes being first or main among several options; common in phrases like 'primary goal/concern/reason/source', often implying other secondary ones exist.

  强调在若干选项中“排在首位、最主要”，常见于“primary goal/concern/reason/source”等搭配，往往暗示还存在其他次要的选项。

  Her primary concern was keeping the children safe during the storm.

  她最主要的担忧是在暴风雨中保证孩子们的安全。

• important

  The most common, neutral, general-purpose word for anything with great value or effect; freely used in the pattern 'It is important to/that…', which the other three rarely take.

  是表示“有重大价值或影响”的最常见、最中性的说法，可自由用于“It is important to/that…”句型，而其他三个词很少这样用。

  It is important to drink water every single day.

  每天喝水非常重要。

• fundamental

  Stresses that something is a necessary, basic foundation without which the rest cannot exist or work properly; common with 'part', 'principle', 'right'.

  强调某事物是必不可少的根基，没有它其他部分就无法存在或正常运作，常与“part”“principle”“right”搭配。

  Trust is a fundamental part of any strong friendship.

  信任是任何牢固友谊中不可或缺的基本部分。

Cardinal, primary, important, and fundamental all mean very important. Cardinal is very formal, used mainly in fixed phrases like 'cardinal sin'. Primary stresses being first among several options. Important is the common, neutral word, used in 'It is important to...'. Fundamental stresses a basic foundation.

这四个词在此义项上都表示“十分重要”，但语气和搭配不同：cardinal 最为正式，常见于固定搭配（cardinal sin/rule）；primary 强调“众多选项中排在第一位”；important 是最常用、最中性的说法；fundamental 强调“不可或缺的根基”。这里不比较 cardinal 的“红衣主教”“基数”等意思，也不比较 primary 的“小学的”“初选”等意思。