Henry Sweet in his famous grammar of 1891 (p.22), writes:
"In a sentence such as The earth is round, we have no difficulty in recognizing earth and round as ultimate independent sense-units ... Such words as the and is, on the other hand, though independent in form, are not independent in meaning: the and is by themselves do not convey any ideas, as earth and round do. We call such words as the and is form-words, because they are words in form only. When a form-word is entirely devoid of meaning, we may call it an empty word, as opposed to full words such as earth and round."
Content words: noun, adjective, adverb, main verb
Function words: auxiliary verb, modal verb, pronoun, preposition, determiner, conjunction.
According to Prof. John Sinclair, there are two principles at work in language:
The open choice & the idiom principle
The open choice principle
Language is creative
Sentences can be thought of as empty slots
The speaker chooses how to fill each slot
Each choice is a separate one (that is, the choice of words is completely open)
This is the traditional view of language, taught in many pedagogical grammars
The Idiom Principle:
In fact, much of language co-occurs systematically so that words are not chosen individually, but in groups.
Collocation This term covers the notion that there are regularities in how words occur together.
2 key factors:
A) words co-occur
B) the relationships between words have varying degrees of exclusivity
Examples of exclusive relations between words
Blonde
almost only occurs with (collocates with) hair, woman and lady
They collocate strongly
Nice
Nice day, nice salary, nice view – weak collocations
Two kinds of collocation
grammatical/syntactic collocations
E.g. main word + grammatical word (depend + on, acquainted + with)
Semantic/lexical collocations
E.g. two words of equal standing – spend + money, cheerful + face