Non-native speaker here. To me in spoken language both "unicorn" and "hour" have a combination of 2 vowels in the beginning. Let me transcribe them as "ee-oo" and "aa-oo" here.
Why is the aa-oo combination at the beginning of "hour" considered a vowel but the ee-oo in "uniform" is a consonant?
Why is the aa-oo combination at the beginning of "hour" considered a vowel but the ee-oo in "uniform" is a consonant?