A sentence has words in it. What kind of words?
It has nouns: (1a) I looked up and saw the mark on the wall.
and verbs (1b) I looked up and saw the mark on the wall.
It may have adjectives (2a) How readily our thoughts swarm upon a new object…
and adverbs (2b) How readily our thoughts swarm upon a new object…
Such words have a meaning that can be readily explained; these words can be defined. They also have content.
Nouns, verbs, adjectives and adverbs are content words.
But what about the remaining words in our examples above? Take for example the word and. What is its ‘meaning’?
3) I looked up and saw the mark on the wall. Its meaning is in its function in the sentence. It joins together two words, phrases or sentences. It is a conjunction.
A conjunction is a function word. Function words are the kind of words that we leave out when we send telegrams, when we can guess at the meaning.
Look at this example …saw mark on wall
What words have been left out in this message?
Two occurrences of the word the. We can call the the definite article. What is its function? In example (1), it shows that a unique mark on a unique wall is being spoken about. Virginia Woolf isn’t speaking about ‘a mark on a wall’, that is, any mark on any wall. She’s speaking about a particular, definite mark on a particular, definite wall.
(4) I looked up and saw the mark on the wall. Definite and indefinite articles are function words. What about the words I and our?
(5a) I looked up and saw the mark on the wall.
(5b) How readily our thoughts swarm upon a new object… These are pronouns; they occupy the place of a noun.
But are they, therefore, content words, like nouns? We shall argue that they are not. (Notice that they get left out in telegraphic language.) We can make up new nouns in a language, but we cannot make up new pronouns. Pronouns are a closed set; nouns are an open set. So, we shall say, pronouns are function words. The words that remain in our examples are up, on, upon, and how. The first three are prepositions. Are prepositions content words or function words? We can argue that prepositions have meaning, and treat them as content words. (Notice that they occur in telegraphic language.) Or we can argue that prepositions are a closed set of words like pronouns, and treat them as function words. So this question does not have a single answer. Finally, what is the function of how in our example in (2)? How, we all know, usually asks a question; it is a question word. But our example in (2) is not a question. It is an exclamation. How occurs in the exclamation (2) in place of the intensifying word so in (6a) (6a) Our thoughts swarm upon a new object so readily! (6b) How readily our thoughts swarm upon a new object! How occurs instead of so in (6b) because the emphasised word readily has moved to the front of the sentence. Summing up: Content words are nouns, verbs, adjectives, adverbs, and perhaps prepositions. Function words include conjunctions, pronouns, determiners and demonstratives, quantifiers and intensifiers, question words, and perhaps prepositions.