transition

Concise Oxford English Dictionary © 2008 Oxford University Press:
transition/tranˈzɪʃn/

▶noun

• 1 the process or a period of changing from one state or condition to another.

• 2 Music a momentary modulation.

▶verb chiefly N. Amer. undergo or cause to undergo a transition.

– derivatives
transitional adjective,
transitionally adverb,
transitionary adjective.

– origin C16: from Fr., or from L. transitio(n-), from transire ‘go across’.