Without the introductory word, a dependent clause would instead be…
An independent clause
A dependent clause can function as
Noun
Adjective
Adverb
These 11 words can begin a noun clause
who whom whose which that
when where whether
how why what
Noun functions
Subject
Predicate nominative
Direct object
Indirect object
Object of the preposition
Appositive
These 7 words ca begin an adjective clause
Who
Whom
Whose
Which
That
When
Where
These types of adjective clauses do not take punctuation
Essential adjective clause
‘That’ clause
These types of adjective clauses need punctuation
Nonessential adjective clause
Removed adjective clause
This type of clause begins with a subordinate conjunction
Adverb clause
A dependent clause in which the subject and/or verb is missing
Elliptical clause