I always forget a few grammar rules and can’t seem to get them remembered so I wrote an Elisp snippet to help me remember. Langtool catches this but it isn’t worth waiting. It seems silly to me to write a reminder, but, I bet hundreds of us Emacs users face this. The definition is my own, and includes my opinion about how not to use both words!
(defun affect-vs-effect-explanation () "Definition and example of the most frequent use of Affect vs. Effect." (interactive) (let* ((title "Affect Versus Effect") (sep (make-string (length title) ?=)) (buf (get-buffer-create (concat "*" title "*")))) (switch-to-buffer buf) (insert (concat title "\n")) (insert (concat sep "\n\n")) (insert "Affect is a verb. It means \"to have influence upon\". In the present tense affect is followed by a noun in the form of \"X affects Y\". For example \"Choosing between tabs or spaces for indentation affects our happiness.\" In the past tense it is followed by a preposition before the noun. For example \"Most people are deeply affected by the their choice between using tabs or spaces for indentation.\" Effect is a noun. It is an outcome or result of a verb. For example \"Choosing spaces for indentation had a positive effect on her happiness.\" There are other definitions for affect and effect and you probably shouldn't use them.") (help-mode) (setq buffer-read-only t)))