English to Portuguese Medical Medical (general) Distúrbios

I am thinking of words such as a, is, are, one, two, said, again, been, could, the, and once, which pop up frequently in books for young children but don’t seem to follow the rules. Consequently, they must be committed to memory and recognized on sight; not surprisingly, they are often referred to as **sight words**.
Eu compreendo o significado do termo, mas não consigo encontrar o paralelo ou a tradução consagrada em português (BR). A explicação do termo é:
Sights words are words that are recognized by sight rather than sounded out, in order to achieve reading fluency. They are the most frequently used words in the English language, and are often unable to be read phonetically. ("Was", "are", and "out" are examples.) Sight words are taught in school beginning in kindergarten, and extend up through early elementary. Teachers often send lists of words home for parents to practice with their children, as readers must ultimately memorize the words in order to read fluently and with full comprehension.
Obrigada.