O

[on words]

See: [PLAY ON WORDS].

[on your life]

See: [NOT ON YOUR LIFE].

[on-again, off-again]

See: [OFF-AGAIN, ON-AGAIN].

[once]

See:

[AT ONCE],

[EVERY NOW AND THEN] or [EVERY ONCE IN A WHILE].

[once and for all]  {adv. phr.}

1. One time and never again; without any doubt; surely; certainly; definitely.

Let me say, for once and for all, you may not go to the party Saturday.

For once and for all, I will not go swimming with you.

2.  […]

[once bitten, twice shy]

See: [BURNT CHILD DREADS THE FIRE].

[once for all]

See: [ONCE AND FOR ALL].

[once in a blue moon]  {adv. phr.}

Very rarely; very seldom; almost never.

Coin collecting is interesting, but you find a valuable coin only once in a blue moon.

* /Once in a blue moon someone grows a very pale marigold, but no truly white  […]

[once in a while]  {adv. phr.}

Not often; not regularly; sometimes; occasionally.

We go for a picnic in the park once in a while.

Once in a while the puppy would run away, but usually he stayed in the yard.

Syn.: [AT TIMES], [FROM TIME TO  […]

[once upon a time]  {adv. phr.}

Sometime before now, long ago.

Once upon a time she was thought to be the most talented actress in the country.

- Often used at the beginning of fairy stories.

* /Once upon a time there lived a king who had an ugly  […]