once

One time only.

• I have been there once.
• We meet once a week.
• Please say that once again.

How to use it: once a day/week/month (We water the plants once a week.)

Similar words: one time

Common phrases: only once, once again, once a week

At a time in the past, although usually no longer true.

• This building was once a school.
• I once knew a man who kept snakes.
• She was once very famous.

Similar words: formerly, previously

Common phrases: once famous, once lived, once knew

After something happens or becomes true.

• Once you finish, you can leave.
• Call me once you get home.
• Once she understood the rules, the game was easy.

How to use it: once + clause (Once the rain stops, we can go outside.)

Similar words: after, as soon as

Common phrases: once ready, once you finish, once it arrives

After a particular event or action has happened.

• Once finished, the cake needs to cool.
• Once back home, we unpacked our bags.
• Once the work is completed, we can relax.

How to use it: once + clause (Once I have packed, we can leave.); once + past participle (Once signed, the agreement cannot be changed.)

Similar words: after

Common phrases: once finished, once completed, once back home

One time in a stated period.

• We go swimming once a week.
• She visits us once a year.
• Take this medicine once a day.

How to use it: once a day/week/year (They meet once a month.)

Similar words: one time

Common phrases: once a day, once a month, once a year

At an earlier time, but no longer now.

• We were once friends.
• She was once a teacher here.
• This quiet village was once a busy port.

Similar words: formerly, previously

Common phrases: once friends, once wealthy, once a teacher