What is a prefix for the word large?

There isn't a common, single-word prefix that means "large" in English. However, there are prefixes that can be used to create words with a similar meaning, depending on the context:

* Mega-: This prefix denotes something extremely large or powerful, as in "megacity" or "megastore".

* Macro-: This prefix refers to something large in scale or scope, as in "macroeconomics" or "macroevolution".

* Grand-: This prefix emphasizes size or importance, as in "grandiose" or "grandmaster".

* Super-: This prefix denotes something exceptionally large or powerful, as in "supermarket" or "superman".

The best prefix to use will depend on the specific meaning you want to convey.