English spelling is rather confusing, to put it mildly. Native speakers spend (or used to, anyways) years mastering and memorizing the order of letters for a given meaning. It is not just an intellectual exercise either. I have no hair is rather a different problem than I have no heir or even I have no hare. Not having a good visual memory, I often struggled with able versus ible. Do I drink potable or potible water? Being born before the day of Office Spell Check, I had to either look in the dictionary or discover a rule.
The rule I found, which works most of time, is that able follows an actual verb while ible follows a root, noun, or adjective. For example, learning English is both feasible and doable. It is also both reasonable and sensible to learn other languages.
You will many ibles in this verse from the song “When you are old and grey” by the great American musical satirist (and math professor from my alma mater, the University of California at Santa Cruz):
“An awful debility, a lessened utility, a loss of mobility is strong possibility. In all probability, I’ll lose my virility and you your fertility and desirability. And this liability of total sterility will lead to hostility and sense of futility. So let’s act with agility while we still have the facility for we’ll soon reach senility and lose the ability.”
All the “able-bodied” words follow the rule.
To end this blog, I’ll cite the end of the song:
“So please remember, when I leave in December, I told you so in May.”