Since I heard that "He climbed the mountain up" is incorrect, I've been asking people why that is.
The composition He (Subject) + climbed (transitive verb) + the mountain (direct object) + up (adverb) looked correct to me.
Many people answered my question saying that it is incorrect because the word "Up" is not an adverb, so putting in "Up" after the direct object, which is adverb's position, makes the sentence incorrect. This was contrary to my knowledge. I have known the word "Up" as an adverb all my life, and every dictionary lists the word "Up" as an adverb with lots of examples. So I thought they were just claiming some grammar that was not commonly accepted and that there was no way "Up" was not an adverb. So I did not really pay attention to their answers and didn't even ask them back why "Up" was not an adverb.
But of the people who answered my question, one or two people explained in detail why "Up" was not an adverb. I couldn't understand their explanation 100%, as I did not know the grammar required to understand their explanation, but their explanation reminded me of all the people who had said "Up" was not an adverb.
Is "Up" an adverb or not? After reading the answers to my previous questions, my understanding is this:
Every dictionary lists "Up" as an adverb and has examples of "Up"'s usage as an adverb. But "Up" doesn't always work the same way an adverb does. In certain cases, "Up" works like an adverb, but in other cases it doesn't. It is an adverb with limitation (or maybe not an adverb at all if all the dictionaries' examples of "Up"'s usage, as an adverb, is actually examples of "Up" as a particle in phrasal verbs?). So placing "Up" after a direct object, when the verb is non-phrasal, transitive verb, is not allowed because "Up" is not an adverb, or even if "Up" is an adverb, it just can't be placed there? (Someone told me putting "Up" in after a direct object makes it sounds as if it is a separated particle. So it adds more to the reason/rule we can't place "Up" after a direct object).
Is that why "He climbed the mountain up" incorrect?
By the way, I know "Up" can be placed after a direct object when the verb is separable phrasal verb and "Up" is a particle.
Although "Throw the ball up"'s meaning is the same as the meaning of each individual words combined, it is still classified as a phrasal verb. So I wonder, does the same rule applies to that?