§ 67. The notions with which thought deals involve many subtle relations and require many nice modifications. Language has instruments, more or less perfect, whereby such relations and modifications may be expressed. But these subsidiary aids to expression do not form a notion which can either have something asserted of it or be asserted itself of something else.
§ 68. Hence words are divided into three classes—
(1) Categorematic;
(2) Syncategorematic;
(3) Acategorematic.
§ 69. A Categorematic word is one which can be used by itself as a term.
§ 70. A Syncategorematic word is one which can help to form a term.
§ 71. An Acategorematic word is one which can neither form, nor help to form, a term [Footnote: Comparatively few of the parts of speech are categorematic. Nouns, whether substantive or adjective, including of course pronouns and participles, are so, but only in their nominative cases, except when an oblique case is so used as to be equivalent to an attributive. Verbs also are categorematic, but only in three of their moods, the Indicative, the Infinitive, and the Potential. The Imperative and Optative moods clearly do not convey assertions at all, while the Subjunctive can only figure as a subordinate member of some assertion. We may notice, too, that the relative pronoun, unlike the rest, is necessarily syncategorematic, for the same reason as the subjunctive mood. Of the remaining parts of speech the article, adverb, preposition, and conjunction can never be anything but syncategorematic, while the interjection is acategorematic, like the vocative case of nouns and the imperative and optative moods of verbs, which do not enter at all into the form of sentence known as the proposition.].
§ 72. Categorematic literally means 'predicable.' 'Horse,' 'swift,' 'galloping' are categorematic. Thus we can say, 'The horse is swift,' or 'The horse is galloping.' Each of these words forms a term by itself, but 'over' and 'swiftly' can only help to form a term, as in the proposition, 'The horse is galloping swiftly over the plain.'
§ 73. A term then may be said to be a categorematic word or collection of words, that is to say, one which can be used by itself as a predicate.