mortal

Compared meaning: causing or likely to cause death (adjective).

比较义项：致命的，会导致死亡的（形容词）。

• mortal 本词

  Literary and dramatic in tone; appears mainly in set phrases like 'mortal wound,' 'mortal danger,' or 'mortal enemy.' Rarely used for ordinary accidents, diseases, or weather; suggests a life-and-death struggle rather than a plain medical fact.

  语气较文学化、戏剧化，主要出现在mortal wound（致命伤）、mortal danger（生死攸关的危险）、mortal enemy（不共戴天的敌人）等固定搭配中；很少用于描述普通事故、疾病或天气，强调生死搏斗的意味，而非单纯的医学事实。

  The spy found himself in mortal danger, surrounded by enemy soldiers.

  这名间谍发现自己身陷生死攸关的危险之中，被敌军包围。

• deadly

  The most general and common word; describes anything with the power or tendency to kill, from weapons and diseases to storms and doses. Neutral in register, used in everyday speech, news, and legal contexts alike.

  语义最宽泛、最常用的词，可以形容任何具有致命危险或致死倾向的事物，从武器、疾病到风暴、剂量都能用；语域中性，日常口语、新闻和法律语境中都会使用。

  The court ruled that the knife qualified as a deadly weapon under state law.

  法院裁定，根据州法律，这把刀属于致命武器。

• fatal

  Describes an event, action, or mistake that actually results, or will result, in death; often used after the fact for accidents, crashes, and illnesses, and figuratively for serious errors, as in 'a fatal flaw'.

  描述已经导致（或将导致）死亡的事件、行为或错误，常用于事后描述事故、车祸和疾病，也可比喻严重的失误（如fatal flaw，致命缺陷）。

  Investigators are looking into what caused the fatal crash on the highway.

  调查人员正在调查是什么导致了高速公路上那起致命车祸。

• terminal

  Restricted to medicine: describes an illness that is incurable and in its final stage, expected to cause death eventually rather than immediately. Used only with words like illness, cancer, or disease, never with accidents or weapons.

  仅用于医学语境，指无法治愈、已到晚期、预计将导致死亡（但非立即致死）的疾病；只能与疾病（illness/disease）、癌症（cancer）等词搭配，不能用于事故或武器。

  Her grandmother was diagnosed with terminal cancer and had only months to live.

  她的祖母被诊断出患有晚期癌症，只剩下几个月的生命。

Mortal, deadly, fatal, and terminal all mean likely to cause death. Mortal is literary, in set phrases. Deadly is most general, for weapons or disease. Fatal means death has resulted in accidents. Terminal means medical: incurable illness. Mortal's and terminal's other senses are not compared.

这几个词都可以表示“致命的”，但语域和搭配不同：mortal文学性较强，多用于固定搭配；deadly是最通用的词，可以修饰武器、疾病、天气等各种事物；fatal强调事件已经导致死亡这一结果，常用于事故和错误；terminal专指医学上无法治愈、已到晚期的疾病。这里不比较mortal表示“凡人的、终有一死的”（如“all humans are mortal”）的义项，也不比较terminal表示“航站楼”或“电脑终端”的义项。

Compared meaning: a human being (noun).

比较义项：人，人类个体（名词）。

• individual

  Treats a person as a single unit set apart from a group, favoring formal, legal, or statistical contexts over casual speech.

  强调把某人当作与群体分开的单独个体看待，常见于正式、统计或法律语境，而非日常口语。

  The contract holds each individual liable for their own debts.

  合同规定，每一个人都要对自己的债务负责。

• person

  The plain, all-purpose word for a human being, used in ordinary everyday speech without special formality or focus on mortality.

  这是指人的最普通、通用的说法，可以用于各种日常语境，没有特殊的正式感，也不强调死亡。

  There's a person waiting outside the door for you.

  外面有个人在等你出去见他。

• mortal 本词

  Stresses that a human being will eventually die, typically used in literary, philosophical, or humorous writing contrasting humans with gods or immortals.

  强调人终有一死，常用于文学、哲理或幽默的语境，用来把人类和神明或不朽者进行对比。

  In the myth, the goddess fell in love with a mortal and faced tragic consequences.

  在这个神话故事里，女神爱上了一个凡人，因此不得不承受后果。

All three can mean 'a human being'. Individual sets a person apart from a group, in formal use. Person is the plain, everyday word for a human. Mortal stresses that a human will die, in literary writing. Not covered: individual as 'single', mortal as 'deadly'.

这三个词在表示“人、人类个体”时容易混淆：individual强调把某人从群体中单独拿出来看待，语气较为正式；person是最普通、中性的说法，日常最常用；mortal强调人终有一死，带文学或哲理色彩，很少用于普通场合。这里不比较individual作形容词表示“单独的，个别的”的用法，也不比较mortal作形容词表示“致命的”的用法。