Choosing between synonyms or near synonyms usually involves choosing between two or more quite dissimilar words. When this has been done, decisions also have to be made about the precise form of a word as it will be entered in the thesaurus. Aspects of the exact form of an entry term cover a range of problems, including spelling, punctuation, and the linguistic form of the entry term. From the indexer's point of view, decisions made here do not have quite the same implications for searching as the selection of synonyms, but they are important for the sake of consistency and predictability in the design of the thesaurus. Much of what follows is accepted convention rather than a theoretically based system. Nevertheless there is a strong element of common sense involved, as well as awareness of user searching behaviour.

Grammatical forms Nouns and noun phrases The majority of terms used in thesauri (and in other sorts of subject tool) are nouns or noun phrases. In noun phrases the noun is qualified by an adjective or another noun, or more unusually a preposition links two nouns – very, very occasionally an adverb may occur:

Adjectives and adverbs

Except where they form part of an adjectival or adverbial phrase of this kind, adjectives and adverbs are not used as entry terms in the thesaurus, and they can never stand alone.

Verbs

A great number of the terms in the thesaurus will be activities or actions of some sort. The verbs necessary to represent them can be used in a restricted way, that is in the form of verbal nouns and gerunds. The infinitive form of the verb (to organize, to manage, to operate, to cook) and the past and present participles (organized, organizing, managed, managing, operated, operating, cooked, cooking) are never used, except where participles are used adjectivally in phrases (Organized crime, Managed learning environment, Operating systems, Cooked meats).

Conversion to the appropriate noun form is necessary for inclusion in the thesaurus.