ref – https://www.englishwithashish.com/adverbials-masterclass/#google_vignette

What is an adverbial clause?

An adverbial clause is a dependent clause that functions as an adverb in a sentence.
This means that it cannot stand on its own as an independent sentence.

It gives more information about the

• time
• place
• condition
• reason
• manner
• purpose of the action

It modifies

• verb
• adjective
• adverb

An adverbial clause contains a subject and a verb

Adverbial Clause format and usage

adverbial clause (dependent clause): subordinate conjunction + clause
[]: main clause

Adverbial clause of time:
[He drinks coffee] before he leaves his house.
*modifies ‘drinks’. What does he always do before he leaves? Drinks coffee.

Adverbial clause of time:
[We’ll be sitting in the conference room] until they tell us to leave.
* modifies “sitting”. When/What time will they be sitting? Until someone (maybe security guard) tells them to leave.

Adverbial clause of manner:
As dollar signs flashed in his eyes, [my brother agreed to the deal].
*modifies ‘agreed’. How did he agree? In the manner that dollar signs flashed in his eyes.

Adverbial clause of manner:
[She addressed the crowd] as she had practiced in the mirror.
*modifies ‘addressed’. How did she address the crowd? The same way she practiced in the mirror.

Adverbial clause of manner:
[José], as he tried to contain his excitement, [waited for her response].
*modifies ‘waited’. How did Jose wait? Very excitedly.

Adverbial clause of place:
[My son told me another fight broke out] where he eats lunch.
*modifies ‘broke out’. Where did it break out? Where he eats lunch.

Adverbial clause of place:
[They drove] beyond where the city ends.
*modifies ‘drove’. Where did they drive to? The place where the city ends.

Adverbial clause of concession:
Whether my friend likes it or not, [we’re going on the roller coaster].
* modifies entire clause ‘We’re going on the roller’.

Adverbial clause of reason:
[We adopted these two cats] because they are cute.
* modifies ‘adopted’. The reason why you ‘adopted’ was because they are cute.

Adverbial clause of reason:
[He is amazing at soccer] because he spent his youth at the AYSO..
*modifies ‘amazing’. The ‘because’ explains why he is ‘amazing’.

Adverbial clause of reason:
[I took out the trash] because it stunk.
*modifies ‘took out’. What’s the reason for taking out the trash? Because it smelled terrible!

Adverbial clause of result:
[It was dark], so Nina lit a candle.
*modifies the main clause ‘It was dark’. It was dark and as a result, Nina lit a candle.

Adverbial clauses of manner (as, as if, as though, like):

He [sings] as if he were a professional. (manner)
The adverbial clause modifies the verb “sings” by describing how he sings.

He talks as if he knows everything. (Compares his manner of speaking to someone who knows everything)
She dances as though she’s floating on air. (Describes her manner graceful way of dancing)
He talks as if he’s an expert. (This describes the manner that he talks, as if he were an expert.)
It looks as though it might rain. This compares the manner of the weather to the appearance of impending rain.

A word on ‘like’

Note that like can be used as a conjunction.

Usually, we use ‘like’ as preposition:

“She looks [like] her mother.” Here it’s NOT introducing a clause with a subject and verb.

When used as part of an Adverbial clause, it is used as a conjunction:

The cake tastes [like] [it(s) has(v) almonds in it]. (Adverbial clause of manner, modifying “tastes”)
He talks [like] [he(s) knows(v) everything]. (Adverbial clause of manner, modifying “talks”)
He spends money [like] [he(s) is(v) a millionaire]. (Adverbial clause of manner, modifying “spends”)

“Like” as a Preposition

Role: It compares two nouns or pronouns, showing similarity.
ex: She looks like her mother. (comparing two nouns)

Structure: It’s followed by a noun or pronoun (the object of the preposition). It doesn’t introduce a clause with a subject and verb.  
Examples:
I enjoy fruits [like] [apples and oranges]. (the two fruit nouns follows ‘like’)

“Like” as a Conjunction (Informal)

Role: It introduces a dependent clause that shows a comparison or manner. This clause has its own subject and verb.
Structure: It’s followed by a subject and verb, forming a clause.

Examples:
He acts [like] [he(s) is(v) the boss].
It sounds [like] [it(s) is(v) going to rain].

Adverbial clauses of place (where, anywhere, everywhere):

Where the river flows, the land is fertile. (The clause describes the location of fertile land.)
Wherever you go, I will follow. (The clause expresses an action that happens regardless of the location.)
You can sit anywhere you like. (The clause indicates freedom of choice in seating location.)
Everywhere I look, I see signs of autumn. (The clause emphasizes the pervasiveness of autumnal signs.)

Adverbial clauses of condition (if, unless, provided, as long as, in case, on condition that):

if: This is the most common conjunction for conditional clauses. It expresses a possibility.
Example: If it rains, we’ll stay inside.

If you study hard, you will [pass] the exam. (condition)
The adverbial clause modifies the verb phrase “will pass” by stating the condition required to pass.

unless: This means “if not” or “except if.”  
Example: We’ll go to the beach unless it’s too cold.

provided (that): This expresses a condition that must be met for the main clause to be true.  
Example: You can borrow my car provided that you return it by tomorrow.

as long as: Similar to “provided that,” it sets a condition that needs to be fulfilled.  
Example: You can stay here as long as you like.

in case: This expresses a condition that might happen, and the main clause describes what to do if it does.
Example: Take an umbrella in case it rains.

whether…or: This presents two alternative conditions.  
Example: Whether you like it or not, you have to go to school.

Adverbial clauses of reason

Because she was tired, she [went] to bed early. (reason)
* The adverbial clause modifies the verb phrase “went to bed” by explaining why she went to bed early.

Since it was raining, we decided to stay indoors.
* modifies ‘decided to stay’. It explains the reason they ‘decided’ to stay in doors.

Seeing that the weather was nice, they decided to have a picnic.
* modifies ‘decided to have’

Note that it’s introduced by “Seeing that”, which acts as a conjunction to connect the adverbial clause to the main clause:

seeing (that) / considering (that): These phrases introduce a reason or cause. “Seeing” and “considering” are present participles.  

Example: Seeing that it’s late, we should go home.
Example: Considering that she’s new to the city, she’s doing quite well.

Adverbial clauses of time

• When the bell rang, the students [rushed] out of the classroom. (time)

  The adverbial clause modifies the verb “rushed” by indicating when the action happened.

Adverbial clauses of purpose (so that, in order that, in order to, so as to, in case, lest)

She studied hard so that she could pass the exam.
They woke up early in order to catch the first train.
I’ll leave a note in case he forgets.

Adverbial clauses of comparison (of degree and manner)

Adverbial clause of concession

Although it was raining, they [decided] to go for a walk. (concession)

The adverbial clause modifies the verb phrase “decided” by a concede. I admit that it is raining, but I still went for a walk.

Each type communicates different information, but every type is a group of words that functions as an adverb.

Adverbial Clause modifying Adverbs

• She spoke so softly that I could barely hear her.

  Adverbial clause: that I could barely hear her
  Modified adverb: softly
  The clause explains to what extent she spoke softly.
  

• He drives more carefully when it’s raining

  Adverbial clause: when it’s raining
  Modified adverb: carefully
  The clause describes under what condition he drives carefully.
  

• They arrived earlier than we expected.

  Adverbial clause: than we expected (them to arrive) – This is an elliptical clause with some words implied.
  Modified adverb: earlier
  The clause shows the degree of earliness by comparing it to our expectations.
  

• I completed the task more quickly than my brother did.

  Adverbial clause: than my brother did (complete the task) – Another elliptical clause.
  Modified adverb: quickly
  The clause provides a comparison to show how much quicker the speaker was.
  

• She sings more beautifully when she’s on stage.

  Adverbial clause: when she’s on stage
  Modified adverb: beautifully
  The clause explains the condition under which she sings more beautifully.