A transitional phase or period is when something changes from one state to another. It's like being between two things.
When we talk about a transitional period, usually we mean that it's a time of change or adjustment. For example, if you're moving to a new city for college, the summer before classes start can be a transitional time - you're leaving home and getting used to your new place but not yet fully settled into campus life. Sometimes people use transitional when talking about education, like discussing how high school is a transitional period between childhood and adulthood.
If we think about it, the word "transitional" has two main uses based on its part of speech. As an adjective, it describes something that's happening or changing from one state to another, like a country transitioning from a dictatorship to democracy. As a noun, a transitional can be a special building or area in an airport where passengers wait for their connecting flight. This kind of transitional usually has amenities and services available so travelers can rest or work while they wait.
of, or relating to a transition
Example: transitional justice
