"No modern grammar claims that there are eight parts of speech."
So, do you agree with that statement? Old school says that each and every word, phrase, and clause in a sentence is acting as a single part of speech.
"I ran to the store to buy a cool bottle of soda because I was really thirsty."
Aren't all these words a part of speech? Do you believe that the two phrases and the one subordinate clause each act as one word? No? Then I say no more to say to you, for your rejecting the fundamental principles of our language which is structured in such way to give meaning and purpose to every single word in a sentence.
words: I is a pronoun; ran is a verb
phrases: to the store (prep phrase); to buy milk (infinitive phrase)
sub clause: because I was really thirsty
"to the store" is a group of words; what word would you say comes to our mind when you see this phrase? Look at it carefully "to the store" What word do you think best describes this phrase? Maybe the word, "going" like in "going somewhere"? This is the basic idea behind the phrase and clause.
"because I was really thirsty." Again, can you think of one main word that comes to mind? I can. "thirst" You see, once you read the words and grasp the main idea (word) in your mind then the rest of the words fill in the rest of the picture. That's about it.
Does this make any sense to you? It's not easy at first.
I took the test while I was still thinking about the argument I had with Phillip this morning.
"while I was still thinking about the argument I had with Phillip this morning" One word. One idea supported by other words, but still one idea, one word in itself. My idea for this one? argument, and the rest answers and describes and explains "argument"-- When, who. what ,why, where, how. If you can't get this, and I know you haven't yet, you'll never understand our language to its fullest.
Or a prepositional phrase: He came from under the bed! = compound preposition e.g. according to; in addition to; next to; instead of; by means of; etc.
Or a clause: It depends on who is coming to the party! = who is coming to the party is a noun clause acting as a single noun and is the object of the the preposition on, which is modifying the verb depends by answering, "Depends on what? or who?"
Or an adverb: Until recently I thought unicorns were real! = until can be a conjunction, but I'll say from the I've seen it used in many sentences, I would say is is more or less idiomatic.
Or an adjective: This is for real! Get real Jack, for real is slang
Or nothing: Who should I talk to?! You got this wrong to begin with: who should be in the objective case whom when it is the object of a preposition. Any question can be made a statement: I should talk to whom. = Whom should I talk to
I know of a nice place to eat. Jack what do you think an adverb answers? These type of questions: where, when, how, why, who, what, etc.
I know of a nice place to eat. What do I know? I know about a place to eat. I also consider it a nice place to dine.
I like him. My mistake. Let's do: I think like him. Now I have an adverb prepositional phrase that answers the question, "Who do I think like?"
You Jack, and a dozen other people here who think they know grammar are at a loss for not understanding basic fundamental concepts structure by rules that give meaning and understanding to our English language. Every single word, phrase and clause in any sentence, whether it's on one word, or two, or implied, serves two main attributes: FUNCTION (NOUN, VERB, ADVERB, ETC.) AND PURPOSE (DESCRIBE, IDENTIFY, QUANTIFY, ETC.). You need to go an get one of them old books, dust it off, and read it before you and a dozen others here pass judgement. And if you read Chicago Manual of Style, Modern Language Association, Associated Press Style Book, Garner's Modern American Usage, and a host of other style and usage books, you find that they have A LOT OF DAMN RULES, NEW RULES AND OLD ONES.
The blind leading the blind. See the light man.