Principles & Parameters Visualizer (X-bar Theory & Move α, after Chomsky, Lectures on Government and Binding, 1981) -- Greg Bryant

Base sentence:

Head-Directionality parameter: Pro-Drop parameter: Movement (Move α):

Speed:

X-bar schema (a universal Principle): XP → Spec X′ ; X′ → X° Complement (or Complement X°, per the Head-Directionality parameter)
Lexicon: N→{man, ball, what} · V→hit · I°→PAST · C°, Spec-CP empty unless filled by movement. Specifiers are always shown to the left of X′ for clarity. “e” = phonologically empty category; “pro” = empty pronominal subject; “t” = trace left by movement.

phrasal projection (XP, X′) lexical head / word landed here via Move α empty category (e, pro, t) being acted on (D-structure)

D-structure (left) → S-structure (right) — hover/tap any node for an explanation