If the first letter of the word after it is pronounced as a vowel (a, e, i, o, u).
an apple
an MP3 player (em-pee-three player)
If you are talking about meteorology, and weather you can use the word front in talking about any changes in temperature that are to occur, i.e. There appears to be a cold front coming towards Rochester.
Use "an" before words that start with a vowel sound, such as "an apple." Use "a" before words that start with a consonant sound, like "a banana." The choice between "a" and "an" depends on the pronunciation of the word, not just its spelling.
According to the media, she is the front runner in the forthcoming election.
I hate when she sashays in front of me!
The fissure gaped in front of me preventing me from going forward.
BOTH..... but it depends on how u use it
You can vegetate in front of the television or you can go jogging with me.
You use the word 'before' to say that something was done at an earlier time compared to something else. For example; I used to have my breakfast before going to school everyday. You use the word 'in front of' to demonstrate a position, i.e that something is by position, in front, compared to something else that is behind the former. For example; I sit in front of Aaron in our Contract Law class.
In this case, you would use the word 'more' in front of 'perpetual' to indicate the comparative form.
My parents always try to heckle in front of people.
The mailman trundled the heavy box to the front door.
He placed his favorite plant in an urn in front of his house.