Tapan is the name given to a Vulcan symbol. The English translation is Process. Together with the symbols Rata (Concept) and Tafar (Discipline), Tapan completes a trinity of Vulcan symbols commonly displayed on clothing such as the robes Spock wears when he arrives on the USS Enterprise in Star Trek: The Motion Picture.
Concept, Discipline, Process. A more poetic rendering of this trinity is "Branches entwined form the tree."