Because modern English has shed most of the flexional endings that distinguished grammatical functions and because English word order is more fixed than ever before, many of our words possess the lively ability to rail-jump from one part of speech to another without any basic change in form. This happy facility, variously called function shift or conversion, endows our language with vitality, power, and a prolific source of new words.
Word Ways: Vol. 12
, Article 4.
Available at: http://digitalcommons.butler.edu/wordways/vol12/iss2/4