Prepositions are very common words. Seven of them are in the top 20 words in English. Prepositions link a word to another part of the sentence and tell us what the relationship is, for example in space or time.
These are the most common fifty irregular verbs in the English language. This does not include the auxiliary verbs "do" and "have". Just by learning these fifty, your students will have prepared themselves for 87% of irregular verb use in English!