Expressing frequency simply 
- We sometimes go out for a drink after work.
- I play tennis twice a week.
- I often skip lunch.
The expressions in red are adverbs (or adverbial phrases) of frequency. They provide information on how often — how frequently — something happens. The information they give us is either indefinite (not mentioning specific points in time) or definite (specific).
Indefinite frequencyThe most common adverbs of indefinite frequency are:
never (0%) | rarely | sometimes | often | usually | always (100%)
The line shows increasing frequency. “Never” indicates a frequency of 0 per cent, and “always” a frequency of 100 per cent, while the others are in between.
Other examples, also in increasing frequency, are:
seldom | occasionally | frequently | regularly | normally | generally
Ever
The word “ever” is also an adverb of indefinite frequency. It means “at any time” and is used mainly in questions, sentences with a negative meaning and if-sentences:
- Have you ever met Bob Rhodes?
- She is hardly ever friendly.
- Please let me know if you ever need my help.













COMMENTS
Dear Sir or Madam,
I have just done the test where you have to put the words and adverbs in the right place to get the correct sentence.
One of the correct sentences is:
I usually have to work on Saturdays.
According to your given rule, the adverb "usually" should go before the main verb or after the first auxiliary verb in a clause or sentence.
Does "have" stand here for a main verb?
Thanks for your explanation as I am a bit confused now.
Best wishes
Sigrid Schuster
Yes, here "have" is the main verb.
Best regards
Deborah Capras