Scope of Declarations

Elements declared in a module (declarations) are visible only:

• In the templates of other elements declared in the same module.
• In the templates of modules that import this module and that export those elements.

Conversely, a component declared in module A cannot be used directly in the template of a component in module B unless:

• Module A exports that component, and
• Module B imports module A.

This encapsulation avoids naming collisions and clarifies dependencies.

Example:

// module A
@NgModule({
  declarations: [CompA],
  exports: [CompA],
})
export class ModuleA {}

// module B
@NgModule({
  declarations: [CompB],
  imports: [ModuleA], // now CompA is usable in CompB's template
})
export class ModuleB {}

If CompA were not exported, ModuleB could not use it, even by importing ModuleA.

Note: In a standalone‑component architecture, this notion of scope is replaced by direct imports of components in templates (imports array of @Component), making visibility more explicit.