177. Special rules for a or an are the following:—

1. Before words beginning with the sound of y or w, the form a, not an, is used.

Examples:

This rule covers all words beginning with eu and many beginning with u. Note that the initial sound is a consonant, not a vowel. An was formerly common before such words (as,—an union, such an one), but a is now the settled form.

2. Before words beginning with h and not accented on the first syllable, an is often used. Thus, we say—

In such cases, the h is very weak in sound, and is sometimes quite silent, so that the word practically begins with a vowel. Usage varies, but careful writers favor the rule here given. An was formerly more common before h than at present.

178. With two or more connected nouns or adjectives the article should be repeated whenever clearness requires (cf. [§ 123]).