occasional

Compared meaning: happening now and then, not regularly (adjective).

比较义项：偶尔发生、不规律或偶然出现的（形容词）。

• occasional 本词

  Describes something pleasant or neutral that happens now and then, at scattered but unremarkable times; almost always used before a noun (an occasional treat), never as a predicate like 'became occasional'.

  表示某种令人愉悦或中性的事情偶尔发生、间隔不固定；几乎总是放在名词前作定语（an occasional treat），不能像 irregular 那样直接作谓语（不说 became occasional）。

  He treats himself to an occasional slice of chocolate cake.

  他偶尔会犒劳自己吃一块巧克力蛋糕。

• irregular

  Focuses on an unsteady rhythm or timing rather than simple infrequency; can describe something happening often but unevenly, and unlike the others can stand alone as a predicate (his heartbeat was irregular).

  强调节律或时间安排不稳定，而不只是“不常发生”；可以描述频繁但不均匀的情况，并且和其他几个词不同，可以单独作谓语（his heartbeat was irregular，心跳不规律）。

  Her sleep schedule became irregular after she started the night shift job.

  她开始上夜班后，睡眠安排变得不规律了。

• stray

  Describes one isolated occurrence that happens purely by chance and stands apart from any pattern; typically modifies a single physical object, remark or thought rather than describing frequency.

  指单一的、纯属偶然、脱离任何规律的个例；通常修饰单个具体的事物、话语或念头，而不是用来描述发生的频率。

  A stray bullet shattered the window during the late-night celebration.

  深夜庆祝活动期间，一颗偶然飞来的子弹打碎了窗户。

• sporadic

  Emphasizes isolated bursts of activity that surface now and then over a stretch of time, often with a mildly negative or noteworthy tone, and typically describes an ongoing situation rather than one single object.

  强调在一段时间里断断续续地爆发或出现，常带一点负面或值得关注的语气，通常描述持续存在的状况，而不是单一的一件事物。

  Sporadic fighting broke out along the border throughout the ceasefire.

  在停火期间，边境沿线断断续续地爆发了零星的战斗。

All four mean something happens now and then, not regularly. Occasional is neutral, mostly before a noun. Irregular stresses unsteady timing. Sporadic stresses bursts of activity, often negative in tone. Stray means one chance occurrence, not a frequency. Irregular's and stray's other senses: not compared.

这四个词都能表示“不经常、非固定规律地发生”，但语气和用法不同：occasional 语气中性，偏日常，几乎只作定语；irregular 强调节律或时间安排不稳定，可以单独作谓语；sporadic 强调断断续续、一阵一阵地出现，常带一点负面语气；stray 指单一的、纯属偶然的个例，通常修饰具体事物而非描述频率。这里不比较 irregular“形状不规则的”和 stray“走失的、流浪的（动物）”等其他含义。