Angular - Troubleshooting - BuildErrors

A statement like this

<form [formGroup]="lessonForm"  >

Fails with the error

Can't bind to 'formGroup' since it isn't a known property of 'form'

Summary
[formGroup] is an angular thing

The fix
Make sure the module has the name if the component in the declarations module.

lesson.module.ts
import { NgModule } from '@angular/core';
import { CommonModule } from '@angular/common';
import { FormsModule, ReactiveFormsModule } from '@angular/forms';
import { RouterModule } from '@angular/router';
import { LessonListComponent } from './lesson-list/lesson-list.component';
import { LessonDetailsComponent } from './lesson-details/lesson-details.component';	// ******** Add this
import { SweetAlert2Module } from '@sweetalert2/ngx-sweetalert2';
import { NgxPaginationModule } from 'ngx-pagination';

@NgModule({
  declarations: [
    LessonListComponent, 
    LessonDetailsComponent, // ******** And this
  ],
  imports: [

Other Errors

[[MatFormFieldControlError]] - mat-form-field must contain a MatFormFieldControl