Diffrence between resource and resources!

In the third lesson instead of resource :session if we write resources :session then the test doesn’t pass anyway.
Here in this code if we write resources session then the following code…

Rails.application.routes.draw do
  root to: "todos#index"

  resources :todos, only: [:index,:new,:create]
  resource :session, only: [:new]

… continuously show the following error.

rspec spec/features/user_creates_todo_spec.rb                                                 


  1) User creates todo successfully
     Failure/Error: sign_in
       uninitialized constant SessionController
     # ./spec/support/features/sign_in.rb:3:in `sign_in'
     # ./spec/features/user_creates_todo_spec.rb:5:in `block (2 levels) in <top (required)>'

Finished in 0.02543 seconds (files took 1.77 seconds to load)
1 example, 1 failure

Failed examples:

rspec ./spec/features/user_creates_todo_spec.rb:4 # User creates todo successfully

Why is it looking for SessionController instead of SessionsController ?
Rake routes shows the same routes for both resource and resources and even stack-overflow suggest that the only diffrence is that `resource means resources without index action.

I’m confused. Please help!

Matthew Mongeau explains the difference between resource and resources at the 20:20 mark in the first video of the intermediate ruby on rails series.