Conversion in linguistics is the formation of new words from existing words without a change in form. An example is hoe and hoe. The first one is a noun a hoe, the second is a verb to hoe. Conversion is an established order of word formation in the classification of non-concatenative morphological processes. The other category of word formation in morphological processes is concatenative morphology.
Non-concatenative morphological processes form new words by modifying internal structure of morphemes (e.g., meaning). Concatenative morphological processes form new words by putting morphemes together (e.g., affixation, compounding).