First, let me remind you what a clause is.  A clause is a group of words that consists of a subject and a verb. E.g. He is wearing a red cap. In this sentence, “he is wearing” is a clause because it consists of a subject “he”, and a verb “wearing”.

An adverb is a word which modifies verbs, adjectives, and other adverbs whereas an adverb clause is a subordinating or dependent clause that modifies a verb, adjective or another adverb. So both have the same functions. It almost always starts with subordinating conjunctions. Below is the list of most common subordinating conjunctions.

After, although, as, because, before, even, if, even though, in order that, once, provided that, rather than, since, so that, than, that, though, unless, until, when, whenever, where, whereas, whenever, whether, why, why.

Try to memorize a few of them until you can spot them based on their work in a sentence. 
Let’s we look at some of the examples:

In the sentence, first, we’ve got to find the trigger word which is always at the beginning of a subordinating clause. In our sentence “because” is the trigger word which introduces a dependent or subordinating clause in the sentence. Now we can find the rest of the clause which should consist of a subject and a verb.

In the sentence given above, “he” is the subject and “loves” is the verb. Therefore, “because he loves to play cricket” is our adverb clause. But what does it modify?
As we know an adverb clause can modify a verb, an adjective or an adverb, therefore, our clause cannot modify “he” and “shoes” because these are nouns. It must modify the verb “bought”. Let’s put it to the test using our adverb questions:

• Where
• When
• How
• Why
• To what extent
• In what manner
• Under what conditions.

Bought where? NO ANSWER!

Bought when? NO AGAIN!

Bought why? Because he loves to play cricket.

In this way, we can modify our adverb clauses.

TIP ABOUT ADVERB CLAUSES: When they are at the beginning of a sentence, they are always almost followed by a comma. 

Again first find the trigger word, “EVEN THOUGH”. Because it is at the beginning of the sentence, we can assume that when we get to the comma, we’ve found the adverb clause. So our adverb clause is “Even though I don’t feel like eating” and the rest is our main clause. So what does it modify in the main clause?

It is modifying the word “MADE” in the main clause because there is no other word in the main clause which can possibly be modified. But let’s test it anyway.

Made where? NO ANSWER!

Made when? NO ANSWER!

Made why? AGAIN NO!

Made under what condition? Even though I don’t feel like eating.

Our adverb clause is “because I broke her mobile”. What does it modify in the main clause? Since adverb can neither modify a noun or a linking verb, therefore, it must modify the predicate adjective “Angry”. Let’s test it out.

Angry why? Because I broke her mobile.

Our adverb clause is “because she was ill”. The clause modifies the adverb “slowly” in the main clause. To verify it, let’s put it to the test.

Why slowly? Because she was ill.

In this way, we can spot adverb clauses and also find out which word of the main clause in being modified by the clause using our adverb questions.