lifelong

Compared meaning: lasting for a long time (adjective).

比较义项：持续时间很长的（形容词）。

• lengthy

  Formal word implying something is tediously or excessively long; typically describes meetings, speeches, explanations, or documents.

  较正式的词，暗示某事冗长乏味，多用于会议，演讲，解释或文件。

  The professor gave a lengthy explanation before finally answering the question.

  教授先给出了一段冗长的解释，然后才终于回答了问题。

• long

  The everyday, neutral word for a long duration; combines freely with almost any noun and fits the common phrase 'for a long time'.

  最普通中性的说法，几乎可以搭配任何名词，也常用于“for a long time”这样的短语。

  We've known each other for a long time, since primary school.

  我们从小学起就认识了，已经很长时间了。

• lifelong 本词

  Means lasting for someone's entire life; used only for things tied to a whole lifetime, such as friendships, dreams, or early habits.

  指贯穿一个人的一生，只用于伴随终生的事物，如友谊，梦想或从小养成的习惯。

  They became lifelong friends after meeting in college.

  他们在大学相识后，成为了终身好友。

• endless

  Emphasizes that something feels like it has no end, often used with exaggeration to express boredom, frustration, or impatience.

  强调某事仿佛没有尽头，常带夸张语气，表达厌烦，沮丧或不耐烦的情绪。

  Waiting in that line felt endless, so we finally decided to leave.

  排那个队感觉没完没了，我们最后决定离开了。

Lengthy, long, lifelong, and endless all mean lasting a long time. Lengthy means tediously long, like a speech. Long is neutral. Lifelong means lasting a whole life, for friendships or dreams. Endless feels like it never ends. Not covered: long can mean far away.

这四个词都可以表示“持续时间很长”，但语气和用法不同：lengthy强调冗长，常显得乏味，多用于正式场合；long是最普通中性的说法；lifelong特指贯穿一生，只能用于友谊，梦想等伴随终生的事物；endless则带夸张语气，强调“感觉没有尽头”，常表达不耐烦。这里不比较long表示“距离长”的义项（如a long road）。