Occasional means it happens now and then, with gaps in between. The occasional cigarette, occasional showers in the forecast, an occasional visitor who turns up twice a year.
The most useful shape is 'the occasional' followed by a singular noun: 'She has the occasional glass of wine' means a few, well spread out, and it lands softer than 'sometimes'. The adverb is occasionally, which is the form you will write more. There is a second, older sense as well: made for one particular occasion. Occasional verse is written for a wedding or a funeral, and an occasional table is that small side table in a British living room which exists for whenever a table is wanted. Keep occasional apart from rare, because occasional says regular but infrequent, while rare says hardly ever at all.
1adjectiveoccasionalHappening now and then, with gaps in between.
“There was occasional traffic on the road, but mostly silence.”
synonyms: intermittent, infrequent, sporadic
2adjectiveparticularMade or used for one particular occasion.
“He wrote occasional poems for family weddings.”
Occasional came into Middle English as occasyonal, from Medieval Latin occāsiōnālis and Old French ocasionel, all of it built on occasion. So an occasional event is one tied to an occasion: it comes when there is one, and not otherwise.
Old French
ocasionel
Medieval Latin
occāsiōnālis
Middle English
occasyonal
English, today
occasional
From Middle English occasyonal, from Medieval Latin occāsiōnālis and Old French ocasionel. by surface analysis, occasion + -al.
Etymology from Wiktionary, CC BY-SA