Mutations (séimhiú agus urú)

The beginning of a word in Irish can sometimes be spelt differently and sound different when it comes after certain words.

A few examples of this are:

• when a word comes after a preposition, like ar bhus or i gContae Lú.
• when counting things, like dhá mhadadh or seacht dtábla.
• when a word comes after mo, do, a, ár or bhur to show possession, like mo mhála or ár gcat.

The letters that are placed at the start of words are known as either a séimhiú or an urú.

What is a séimhiú?

A séimhiú lenites, ie makes thinner, the letter at the start of the word, which changes the sound of the word.

In Irish this change is shown by adding a h after the first consonant in the word.

What is an urú?

An urú eclipses the start of the word, which changes the sound of the word just like a séimhiú does, but in a different way.

In Irish, this change is shown by adding a specific new letter before the first consonant in the word. The letter added depends on the consonant that is in the beginning of the word.

Not all words will take a séimhiú or an urú. Words that begin with vowels never take a séimhiú, as well as words that begin with l, n and r. Below is a table of consonants and their changes in spelling.