ἐφάπαξ/ephapax

This word is used to describe an action or situation. It is an adverb.

This word can mean once for all. When used in this way, this word is used to talk about an action or event that happens only one time. This action or event either cannot happen again or never needs to happen again.
This word can mean at once. When used in this way, this word is used to talk about more than one action or situation happening at the same time.