These are all words that begin with the prefix "ad-". However, often the "-d" in "ad-" takes on the consonant of the base word. So if you see longer words that begin with "a-" and have a double consonant after them, the first two letters are often from the Latin preposition "ad" which means "toward".
Whether you’re a teacher or a learner,
Vocabulary.com can put you or your class
on the path to systematic vocabulary improvement.