Final answer:
The breathing mark is placed before the capital vowel at the beginning of a word. It's a rule of orthography in languages such as Greek.
Step-by-step explanation:
When the first letter of a word is a capital vowel, the breathing mark is placed before the vowel. This is a rule associated with the correct punctuation and orthography in certain languages, such as Greek, where breathing marks are used. For example, a word starting with an uppercase 'A' would have its rough or smooth breathing mark placed just before the 'A'.