A prefix is a letter or group of letters added to the beginning of a word to make a new word.
A lot of words in English begin with the prefix ad-, which can mean adding something or moving towards something.
Advent (the time leading towards Christmas)
Another common prefix in English is al-, which means 'all' (but only has one 'l').
In this worksheet you can practise reading and spelling words that begin with the prefixes ad- and al-.