People with serious comprehension difficulties have what is called Wernicke’s aphasia and:
Often say many words that don’t make sense.
May fail to realize they are saying the wrong words; for instance, they might call a fork a “gleeble.”
May string together a series of meaningless words that sound like a sentence but don’t make sense.
Have challenges because our dictionary of words is shelved in a similar region of the left hemisphere, near the area used for understanding words.