Caol le caol agus leathan le leathan

The golden rule for spelling in Irish, caol le caol agus leathan le leathan, means slender with slender and broad with broad. The terms slender and broad refer to two categories of vowels.

The rule caol le caol agus leathan le leathan means that the vowels on either side of a consonant (or group of consonants) should agree; they should both be broad or both be slender. The rule is primarily used when you add an ending to a word (e.g., when conjugating a verb). To satisfy the rule you may need to add a vowel between the word and its ending. Understanding this rule will help you guess the correct spelling so you can look it up in a dictionary. There are a few words that do not satisfy this rule, but mostly they are common words that you probably already know, like anseo and ansin.

Even without knowing a single word of Irish, you can apply the rule to catch many spelling mistakes! Let's try a few examples:

Now you are ready to find spelling mistakes in that letter from your Gaeilgeoir friend.

Note: I originally published this article on E2.