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)))