Sporadic describes something that happens now and then, in a scattered way, with no pattern you can rely on. 'Sporadic rain' means it rains, stops, rains again, and you cannot say when. 'Sporadic gunfire' means shots, then quiet, then more shots. The key idea is not 'rare' — it is 'irregular, scattered, unpredictable'. Something sporadic might happen quite a lot; what it never does is settle into a rhythm. That is worth sitting with, because students often hear it as 'seldom' and lose half the meaning. Compare three neighbours. 'Occasional' means not often — it is about how much. 'Intermittent' means it stops and starts — often used for machines, signals, pain. 'Sporadic' means scattered about with no pattern — and it usually carries a faint sense that this is unsatisfactory, that you wish it were steadier. 'His attendance has been sporadic' is not a compliment. It is a somewhat formal word, at home in news reports, medical writing, and business talk. Doctors also use it in a special technical way: a 'sporadic case' of a disease means one that appeared on its own, not inherited and not part of an outbreak. The adverb is 'sporadically'.