depressed

Compared meaning: feeling sad or unhappy (adjective).

比较义项：感到悲伤、闷闷不乐（形容词）。

• depressed 本词

  The strongest word here, describing a deep, often lasting sadness and hopelessness, sometimes bordering on clinical depression; it is not caused simply by being alone.

  depressed 是三者中语气最重的词，指深沉、常常持续较久的悲伤和绝望情绪，有时接近临床抑郁；这种情绪并不只是因为独自一人而产生的。

  He has felt depressed and hopeless ever since he lost his job.

  自从丢了工作之后，他一直感到沮丧、绝望。

• lonely

  Specifically means unhappy because you are alone or lack company; it names the cause of the sadness (isolation), not just the feeling itself.

  lonely 特指因为独自一人、缺乏陪伴而感到不快乐；它强调的是这种情绪的原因（孤单），而不仅仅是情绪本身。

  He feels lonely at weekends when all his friends are busy.

  周末朋友们都很忙时，他会感到孤独。

• glum

  Describes a sulky, disappointed look or mood, usually after a small setback; milder than depressed and focused on outward expression rather than deep despair.

  glum 描述一种闷闷不乐、失望的神情或情绪，通常是因为一件小事而起；语气比 depressed 轻得多，更侧重外在表现出来的样子，而不是内心深处的绝望。

  He looked glum when his team lost the final in the last minute.

  球队在最后一分钟输掉决赛时，他看起来很闷闷不乐。

Depressed, lonely, and glum all mean unhappy, differing in strength and cause. Depressed is strongest: deep, lasting sadness, near clinical depression. Lonely means unhappy from being alone. Glum means a mild sulky look after a small problem. Not covered: depressed economy, or lonely meaning remote.

这三个词都可表示“不开心、情绪低落”，但语气强弱和原因不同：depressed 语气最重，指深沉而常常持续较久的绝望情绪，甚至接近临床抑郁；lonely 强调不快乐是因为独自一人、缺少陪伴；glum 侧重外表流露出的闷闷不乐或失望神情，语气较轻，通常因一件小事而起。这里不比较 depressed 表示“（经济）萧条的”和 lonely 表示“人迹罕至的，偏僻的”这两个义项。