transition - noun

the act of passing from one state or place to the next

an event that results in a transformation

a change from one place or state or subject or stage to another

a musical passage moving from one key to another

a passage that connects a topic to one that follows

transition - verb

• cause to convert or undergo a transition
• make or undergo a transition (from one state or system to another)

transition - thesaurus

changeover   conversion   modulation   passage