1
general::
rarely
not often:
• These geese are rarely found on inland waters. • 50% of Britons say they rarely eat meat.
not (very) often
often used in everyday English instead of saying rarely:
• Tina’s not often late. • I don't go there very often. • It's not often that you get a chance like this.
seldom
rarely. Seldom is more formal than rarely and is used especially in written English:
• He seldom slept well. • They seldom went out.
hardly ever/scarcely ever
almost never:
• Ben’s nineteen and he’s hardly ever at home these days. • For some reason, her name was scarcely ever mentioned.
very occasionally
used when you want to emphasize that something only happens a few times over a long period of time:
• Very occasionally the temperature drops to below 30.
Longman-Thesaurus