If a word or phrase can substitute a word or phrase in a sentence; that
is, the sentence is grammatical with the substitute, then the
substitute has the same or similar function to the word substituted in
that sentence. Sometimes, we cannot substitute a word or expression in
the same place
in the sentence as another word or expression, although
the substitutions are nonetheless equivalent. For instance, see adjectives,
where an adjective usually precedes a headword, but an adjectival
phrase follows it. Also, it may be necessary to change the person of
the verb.
Nouns
For instance, we can substitute Tom
for Hermonie
in the sentence:
Hermonie went home. Tom went home.
We know that Tom
is a Proper Noun, and because substituting Tom for Hermonie makes a
grammatical sentence, then we can conclude that Tom and Hermonie perform
similar functions in the sentence. In fact, both are Proper Nouns.
Pronouns
We can substitute she for Hermonie in the above sentence:
Hermonie went home. She went home.
Because the sentence is grammatical, we can conclude that she and Hermonie
have a similar function in the sentence. We know that Hermonie is a
Proper Noun, and so she
must be a Proper Noun, or a Pronoun.
Verbs
In the sentence below, we can substitute ran for helter-skeltered:
Tom helter-skeltered down
the road.
Tom ran down the road.
helter-skelter
therefore has a function similar to ran. They are both
verbs.
Adjectives
We can substitute big for black in the following sentence:
The black
cat crossed the road. The big
cat crossed the road.
With adjectives, we might have to substitute a word before a noun with
an expression after the noun.
We saw a tall man. We saw a man who was tall.
We cannot substitute the expression who was tall in
the same place as the adjective tall
in first sentence, but need to put it after the noun man. However, the
expression who was tall
has the same effect as the adjective tall, so it
functions as an adjective.
Conjunctions
If we substitute however
for but in
the following sentence, we get:
Harry was usually mean but
he always gave to charity.
Harry was always mean however he always gave to charity.
Something is wrong. It isn't grammatical. If we read the sentence
aloud, we have to pause before and after however,
to make it sound idiomatic. In speech we have to separate the two
clauses with a pause. In other words, we have to turn them into
sentences. We write this as:
Harry was usually mean;
however, he always gave to charity.
Or
Harry was usually mean.
However, he always gave to charity.
We know and
is a conjunction. It is a word that joins two clauses. And we cannot
substitute however
for and.
So however
does not join two clauses (although ";however," does). It seems that however modifies
the previous sentence. It add information to or takes information away
from the previous sentence. The word however is not a
conjunction, but a linking
adverb.
Tom went home.