An explanation of Adverbs of Frequency, both definite and indefinite, with examples.

1. ADVERBS OF FREQUENCY
Adverbs of frequency tell us HOW OFTEN we do something.
How often do you play football? (it is possible to say ‘when’ instead of ‘how
often’).
They are usually used with the present simple because this is the tense that
tells us about regular activities.
There are 2 types of adverb of frequency: definite and indefinite.
Adverbs of definite frequency
These are usually time phrases that tell us exactly how often we do
something. Examples:
Every week (NOT weeks)
Once a month
Twice a year
Three times a day
Every other hour
On Fridays (‘on Friday’ means one day, ‘on Fridays’ means ‘every Friday’)
Every 4 years
Daily, weekly, monthly, yearly
They usually go at the END of the phrase:
I go to work by car every day.
We play football once a week.
The World Cup is every 4 years.
It is possible, for the purpose of emphasis, to put these adverbs of frequency
at the BEGINNING.
Once a week I make sure to ring my grandparents.
Every day people do good things and bad things.
Daily, weekly, monthly and yearly are not as common and are usually used
with more formal, business-orientated activities. They always go at the end
position:
The company pays its taxes yearly.
We send the invoices monthly.

2. Adverbs of indefinite frequency
Examples:
Always 100%
Often
Usually, Normally, Frequently
Sometimes, Occasionally 50%
Infrequently
Rarely, Seldom, Hardly ever
Never 0%
They tell us how often we do things but without knowing exactly when.
We can always put them in the MIDDLE position: before the main verb (after
the auxiliary) but after the verb BE:
We sometimes go to our friends’ house at the weekend.
I don’t always eat breakfast before I have a shower.
I am never late for appointments.
In this position, you will always be right. However, some adverbs of
indefinite frequency can go in different positions, usually for emphasis. The
most important is ‘sometimes’: it can go at the BEGINNING, MIDDLE AND
END POSITIONS.
Sometimes my parents come and stay with us.
My parents sometimes come and stay with us.
My parents come and stay with us sometimes.
This rule also applies to occasionally, frequently, usually and often.
Rarely can also go at END position (usually with ‘very’):
We see them (very) rarely.
This rule also applies to seldom but it is seldom used.