Is there a prefix or suffix for once?

There isn't a specific prefix or suffix that directly means "once". However, there are prefixes and suffixes that can be used to create words with a similar meaning:

Prefixes:

* Uni-: This prefix means "one" or "single," which can imply a single occurrence. For example, "unicorn" (one horn), "unilateral" (one-sided).

* Mono-: This prefix also means "one" or "single" and can be used in similar ways to "uni-". For example, "monopoly" (one seller), "monotheism" (belief in one god).

Suffixes:

* -fold: This suffix can be used to indicate a single instance or repetition. For example, "onefold" (a single instance), "twofold" (twice), "threefold" (three times).

* -time: This suffix can be used to indicate a single instance of something occurring. For example, "one-time" (a single occurrence), "two-time" (twice).

While these prefixes and suffixes don't directly mean "once," they can be used in specific contexts to convey a similar meaning.

Ultimately, the best way to express "once" depends on the specific context and desired nuance.