You would describe it as "an" orange car. The reason you use the word "an" is because the word orange starts with a vowel. When you are about to use the letter "a", if the word that is after the "a" starts a vowel you have to change that "a" to "an". I hope this helped!

Hi Louis, This is a pretty simple question but one what is often overlooked by teachers and students. In English we have two indefinite articles 'a' and 'an'. 'a' is the most common and normal one to use 'an' is only used when the next sound in the sentence is a vowel sound. So in your example 'an orange car' is correct. It seems pretty simple but there are a few things to remember. First, the 'an' is connected to the next sound in the sentence not the noun. For example 'an elephant' is correct but 'an big elephant' is incorrecnt because 'big' does not start with a vowel sound. Second, the key is a vowel sound not a vowel itself. For example 'I will see you in an hour' is correct. Although 'hour' begins with an 'h' the 'h' is silent therefore 'hour' starts with a vowel sound and so it needs the article 'an' Hope that helps, anymore questions just ask! :)