Frequency
the occurrence of …
the frequency of …
the rate of …
the incidence of …
always
without fail
frequently
repeatedly
in quick succession
a succession of …
… recurs over and again
time and again
time after time
often
regularly
at regular intervals
at 1, 10, 30 etc. minute intervals
every 5 etc. minutes, seconds, years etc.
a five-year cycle
per second
per minute
per hour
hourly
per week
weekly
per month
monthly
per annum
annually
an annual increase of …
yearly
sometimes
occasionally
hardly
seldom
rarely
never
Present
now
the present day
The situation today is that …
the status of …
At present, we are unable to …
at the moment
current theory, knowledge, methods, trends etc.
currently
until now
Recently, …
recent developments in …
as recently as …
Until recently, very little was known about …
… is a relatively recent phenomenon
To date, very few examples of … have been found