mat-form-field' is not a known element angular 10 code example

Example 1: 'mat-form-field' is not a known element

@NgModule({
  imports: [
  	...
	MatFormFieldModule,
    MatInputModule,
    ...
  ]
})

Example 2: 'mat-form-field' is not a known element:

@NgModule({
  imports: [
    MatButtonModule,
    MatFormFieldModule,
    MatInputModule,
    MatRippleModule,
 ]
 ....