Pro-form

A pro-form is a function word that substitutes a word, phrase, clause, or sentence whose meaning is recoverable from the context, and it is used to avoid redundant expressions. A pro-form is also used for the item questioned in a question, and such a pro-form is called an interrogative pro-form.

Pro-forms are divided into several categories according to which part of speech they substitute:

• A pronoun substitutes a noun or a noun phrase with or without a determiner.
• A pro-adjective substitutes an adjective or a phrase functioning as an adjective.
• A pro-adverb substitutes an adverb or a phrase functioning as an adverb.
• A pro-verb substitutes a verb or a verb phrase.

L. L. Zamenhof, the inventor of Esperanto, called a table of systematic interrogative, demonstrative, and quantifier pro-forms and determiners in a language a table of correlatives. The table of correlatives for English follows. Note that while some categories are highly irregular, others (like quantifiers) are not.

		interrogative	demonstrative		quantifier
			proximal	distal	indefinite	universal	negative
determiner		which what	this (sg.) these (pl.)	that (sg.) those (pl.)	some	every	no
pronoun	human	who	this (sg.) these (pl.)	that (sg.) those (pl.)	someone somebody	everyone everybody	no one nobody
	nonhuman	what	this (sg.) these (pl.)	that (sg.) those (pl.)	something	everything	nothing
pro-adverb	location	where	here	there	somewhere	everywhere	nowhere
	source	whence	hence	thence
	goal	whither	hither	thither	somewhither		nowhither
	time	when	now	then	sometime	always everywhen	never
	manner	how	thus		somehow		no-how
	reason	why wherefore		therefore

Some languages may have more categories. For example, while English demonstratives only distinguish proximal (close to the speaker, e.g. this, here) and distal (far from the speaker, e.g. that, there), Japanese makes a three-way distinction between proximal (close to the speaker, e.g. kore, koko), medial (close to the addressee, e.g. sore, soko), and distal (far from both, e.g. are, asoko). Early Modern English made a similar distinction between this/here, that/there, and yon/yonder. Spanish, as well as other Romance languages, shows this same three-way distinction, dating back to Latin.

One of the most salient features of modern Indo-European languages is that relative pro-forms and interrogative pro-forms, as well as demonstrative pro-forms in some languages, have identical forms. Consider the two different functions of who in "Who's the criminal who did this?" or the meanings of that in "That's the man that you saw back home."

Most other language families don't have this ambiguity, nor do several ancient Indo-European languages. For example, both Latin and ancient Greek distinguish the relative pro-forms from the interrogative pro-forms.

See also

• Pro-drop language
• Deixis