Conjugation in the past tense is done by adding a suffix (universal among binyanim), to a binyan-specific root, so that <שמר> "guarded" adds <תי-> "I" to become <שמרתי> "I guarded". The root changes whether the suffix begins with a vowel or consonant. The third person masculine singular pronoun (he/ it) does not take a suffix and uses the plain stem; this is also the dictionary form for any given verb. There also used to be past-tense object suffixes, which came after the subject suffix, but these are obsolete.