Verbs in Hebrew, like nouns, adjectives, and adverbs are formed and declined by altering a (usually) three letter stem. Vowels are added between or before these three consonants in a pattern to form a related meaning between different roots. For instance, "shamar" "(שמר)" "he kept" and "katav" "(כתב)" "he wrote" both add the vowel "a" in between the first and second consonants, and second and third consonants to indicate the past tense "he" form. A similar formation can be found in English strong verbs with write-wrote-written and drive-drove-driven sharing root vowels despite differing consonants and meanings.