The word «conversion» is used to denote a way of word-building which consists in transformation of one part of speech into another.
land (n) àland (v)
step (v) àstep (n)
Today conversion is one of the most productive world-building means. It is a specifically English way of word formation. Its growth was predetermined by the reduction and the subsequent loss of unstressed endings and by the simplification of the morphological structure of the word.
As a result of these changes a number of English nouns and verbs arrived at the same sound and graphic form and became historical homonyms.
OE
ME
NE
lufian (v)
>
loven
>
love (v)
lufu (n)
>
love
>
love (n)
andswarian (v)
>
answeren
>
answer (v)
andswaru (n)
>
answere
>
answer (n)
Historical homonyms such as love (v) and love (n), or answer (v) and answer (n) gradually came to be understood as transformed from one into the other. Such understanding helped to establish a new word building pattern. Verbs were converted to nouns, and nouns were converted to verbs.
The new way of word formation first appeared in late ME, but it reached the peak of its productivity in the NE period.
A great number of nouns were derived from verbs and a great number of verbs were derived from nouns.
Nouns derived from verbs: break, look, walk, jump, help, drive, want, etc.
Verbs derived from nouns: fish, whip, land, hand, dust, etc.