Lecture the word and its meaning

III. Conversion (zero derivation).

Another type of derivation is conversion, or zero derivation. This is a process of coining a new word belonging to a different part of speech without adding any derivative element to the original word. So the basic form of the original word and that of the derived word are homonymous, e.g. Don’t forget to dust the furniture.

As a type of word-building conversion exists in a lot of languages but in English it has developed most intensely due to the lack of morphological signs indicating the part of speech a word belongs to, e.g. home may be a noun (Home, sweet home), an adjective (home assignment), an adverb (go home), a verb (A missile automatically homes the target).
Conversion is the predominant way of forming new verbs in Modern English. They may be formed from nouns (to hand, to shoulder, to knee, to finger, to eye, to nose, etc.), from adjectives (to busy, to slow), from adverbs (to down) and other parts of speech. Nouns may be formed from verbs (a good catch, a short walk, a long drive), adverbs (ups and downs), etc.
A special case of conversion is substantivation of adjectives, i.e. conversion of adjectives into nouns. The degree of substantivation may be full or partial. Fully substantivized adjectives share all the characteristics of nouns: can be used in the singular and in the plural, in the common and possessive cases, with the indefinite, definite or zero articles, e.g. a private, a group of privates, the private’s uniform, privates’ duties. Words female, male, criminal, native, red, grown-up and some others belong to the fully substantivated. Partially substantivated adjectives cannot add –s or ‘s, are always used with the definite article and refer to a group of people, e.g. the blind, the dead, the wounded, the poor, etc.
Most regularly conversion involves simple words but affixed and prefixed words may be converted as well (though less commonly): commission- to commission. Conversion may be combined with compounding, e.g. a drawback, a handout, a take-over, to pinpoint, to blacklist.