In my Phonology of English course I used to give my students a homework task as follows. I am sure the readers of this blog would have no difficulty in answering this question. We all know that the choice between preconsonantal a and prevocalic an is generally determined by pronunciation, not by spelling.
• We say and write an uncle, an urgent message ən ˈʌŋkl̩, ən ˈɜːdʒənt ˈmesɪdʒ but a unit, a Eurocrat ə ˈjuːnɪt, ə ˈjʊərəkræt, because unit and Eurocrat, despite being spelt with an initial vowel letter, begin with the sound j, and in English the two semivowels count as consonant sounds.
• We say and write a house, a heavy weight ə ˈhaʊs, ə ˈhevi ˈweɪt but an hour, an honourable man ən ˈaʊə, ən ˈɒnərəbl̩ ˈmæn, because hour and honourable, despite being spelt with an initial consonant letter, are pronounced with an initial vowel sound (the h being ‘silent’).
There’s a little problem that crops up in words beginning with the letter h in an unstressed syllable: words such as historic and hotel. Nowadays we normally say ə hɪˈstɒrɪk ɪˈvent, ə həʊˈtel. Do we write, correspondingly, a historic event, a hotel? Yes, most of us do. But some people prefer an historic event, an hotel (which to me could suggest a certain literary prissiness or conscious archaizing). Anyhow, both are accepted in writing. The Concise Oxford Dictionary puts it thus:
The h used to be dropped in these words precisely because it was in an unstressed syllable, and in polite Victorian-era English the sound h was apparently restricted to the position before a stressed vowel. A few people, not vulgar h-droppers, perhaps still today pronounce historic(al), historian with no h, at least when preceded by the indefinite article.
So far so good. But over the weekend I was reading the legal judgment in the case before the Court of Appeal concerning the Christian owners of a bed-and-breakfast who had refused a room to a gay couple. The learned justices had frequent occasion in this judgment to use the words homosexual and heterosexual preceded by the indefinite article. And in their written report they chose the form an.
This does seem strange. The initial syllables in these words do not bear the main word stress, but they do bear a lexical secondary stress, which (i) protects the vowel from reduction and (ii) is often realized as a rhythmic beat. I have never previously seen a published (non-dialectal) text that uses an in this position.
I wonder if the judge(s) in question pronounced the phrases with the n when delivering the judgment. I think it unlikely that they would have dropped the initial h.
Interestingly, the legal regulations that the judges quote refer to “a hotel”.