distinct
My daughter went through several distinct stages while learning to read.
early, first, initial, opening, preliminary
advanced, closing, final, last, late, latter, terminal
The project reached its final stage when the team submitted all the required documentation.
critical, crucial, important, key, main
easy
Learning to drive becomes less stressful when your instructor breaks it down into easy stages.
experimental, exploratory
committee, design, development/developmental, formative, planning
The project is in its developmental stage, so we're still making changes.
knockout, semi-final, etc.
The team's loss in the semi-final stage meant they couldn't compete for the championship title.