Once can have multiple meanings depending on the context.

As an adverb, once refers to a single or isolated occurrence of an action, event, or state. It implies that something happened only one time and will not happen again. For example, “I traveled to Paris once.”

As a conjunction, once indicates a cause and effect relationship. It means that one thing happened as a result of another specific event. For instance, “Once you finish your homework, you can go outside to play.”

In computer programming, the once keyword is used to ensure that a certain block of code is executed only once, regardless of how many times it is called. This is often used for initializing data or setting up resources in a program.