When you hear someone say “once” they are referring to some moment in time. The use of “one’s” is a contracted pronoun to illustrate ownership or possession. These are two completely different words with entirely separate meanings, uses and parts of speech.
But both are acceptable depending on how and where you want to use them. There are incorrect and correct usages as well as differences between pronouncing “one’s” or “once.”
“Once” is fairly straightforward. It acts as an adverb to describe the verb of what happens in a particular moment in time, either in the past or the future. Consider the examples below.
Once she decides to return, we’ll go to the movies. [future implications – describes “when” she will decide to return]
Take the cookie sheet out of the oven once the timer goes off. [future implications – describes “when” the timer will go off]
Once upon a time, there was an ugly old witch in the woods. [past implications – describes “when” there was an ugly old witch.]
He went to the races once, he didn’t enjoy it. [past implications – describes “when” he went to the races]
Usage of “One’s”
When you use “one’s,” this is a pronoun indicating possession. It has nothing to do with time and there is no indication of male or female, it is both or either. The following sentences illustrate proper usage.
One’s property is a reflection of one’s willingness to work.
Should a person decide to travel, one should always keep track of one’s luggage.
Five minutes away from a smartphone each day will save one’s sanity.
One’s right to speak should never experience censorship.
There are a couple of simple and easy tricks to remember the difference between using “once” and “one’s.”
Once (adverb) – Time
One’s (pronoun) – Possession
A tip you can employ for “once” is by replacing it with “when” (as in the examples above). If you can put “when” where “once” should be and it makes sense, this is the right form. There are also some pronunciation differentiations too. “Once” has an ‘s’ sound at the end whereas “one’s” has a ‘z’ sound.
“Once” is an indication of time that acts as an adverb to describe the verb of the sentence’s subject. “One’s” is a possessive pronoun that has no specific gender attached to it.