It has been shown that you can fail to recognize as many as one in every hundred words and still understand the passage well enough to read it independently. When you cannot understand the passage any longer, then you must stop to consult a friend, a parent, or a dictionary. When you learn the meaning of the word that you need, read on again. When you are finished reading, you can do what life long learners of vocabulary do. They refine their understanding of the words that they come across by studying them later.
Many readers lightly underline the words that they want to examine at a later date.
At that time, they look them up in a dictionary with the idea of learning the precise meaning of the word, its pronunciation, and relationship between its word elements and its meaning. Some people concentrate on learning a word a day. They try to use it verbally and in writing at least once during the day. Others create flash cards and review them periodically. On your journey toward a more powerful vocabulary.