When learning a second language, people usually learn the written form at the same time as the spoken form. With English, this can be confusing because the spelling is very irregular. This is especially true for the rule about when to use a versus an, but if phrased in terms of pronunciation rather than spelling, the rule is extremely simple:
RULE: Use a before words beginning with a consonant sound and an before words beginning with a vowel sound.The spelling often agrees with the phonetic rule, as in the following example:
- a cat
- an old cat
- a university (because university begins with the y sound of youth)
- an umbrella (because umbrella begins with the u sound of up)
- a xylophone (because xylophone begins with the z sound of zoo)
- an x-ray (because x-ray begins with the e sound of extra)
- a hat (because the h is pronounced)
- an hour (because the h is silent)
Note that there are a few people who believe that an should be used before certain words that begin with an h sound in modern English, and consider this 'proper' educated usage. The most common example of this occurs with the word historic:
- an historic event (rare usage)
In general, if native speakers have to be taught a rule that doesn't come naturally, there is probably something fishy about the rule. Misguided rules of this kind are almost not worth mentioning, except that people benefit from an awareness of them when they, for example, end up working for people who believe them.
THE versus THE
Like a, the pronunciation of the varies depending on whether the next word begins with a vowel or consonant sound. Before a word beginning with a consonant sound, the vowel of the is usually reduced to what's called a schwa, represented by the ə symbol in the International Phonetic Alphabet:
- the cat (pronounced ['ðə] with a short middle vowel)
- the old cat (pronounced ['ði] to rhyme with bee)