What is the adjective in the following sentence I am holding a marker in your left hand?

First, the pronouns need to agree-- I am holding a marker in "my" left hand. In this sentence, the Word "my" and the Word "left" become adjectives, because they are describing the noun "hand." If you wanted to describe the other noun (marker), you could say you were holding a "yellow" marker or a "large" marker. An adjective tells us more about the noun it is modifying.