Is it a horse or an horse? “A horse” is correct. The article is always used before a noun but according to pronunciation, Article “A” is used for consonant pronunciation and Article “An” is used for vowel pronunciation.
Is it a uncle or an uncle? You will always use “a” before a consonant sound and “an” before a vowel sound, which is why “a uncle” is incorrect while “an uncle” is correct.
Is it a ant or an ant? An ant is correct. ‘An’ is used before words beginning either with a vowel or a vowel sound.
Is it a eagle or an eagle? We used the term ‘eagle’ for the first time in the text. So, we are talking about ‘eagle’ in general and not pointing out to a specific eagle here. Thus, we need to use an indefinite article and since the word ‘eagle’ begins with a vowel sound, we should use the indefinite article ‘an’.