Grammar

Question 1

When to use a or an?

Answer 1

The basic rule for using a in a sentence is

Use a before words, abbreviations, acronyms, or letters that begin with a consonant sound, regardless of their spelling.

For example, A dog. A fish. A university. A utopia.

The important part is the sound of the word that follows, not necessarily the letter with which it starts. The above examples have words that begin with vowels and consonants, but we use a for all of them because they begin with the sound of a consonant.

When to Use An

An is used before words, abbreviations, acronyms, or letters that begin with a vowel sound, regardless of their spelling.

An idiot. An element. An honor. An heirloom.

Question 2

Than versus then, how to choose ?

Answer 2

Than is used to make comparaison.

He is taller than I am.

She can run faster than I can.

Your meal looks better than mine does.

Coca-Cola is better than Pepsi.

Then is for all the other cases.