Yes, ‘quieter’ is indeed a word. It is the comparative form of the adjective ‘quiet.’
In English, we often form comparatives by adding ‘-er’ to adjectives. This means that when we want to compare two things in terms of their level of quietness, we use ‘quieter.’ For example, you might say, ‘The library is quieter than the café.’ This use of the comparative allows us to indicate that one place is less noisy than the other.
Additionally, ‘quieter’ can also be used in grammatical constructions where we express varying degrees of quietness. It’s worth noting that while ‘quieter’ is correct, in some contexts or dialects, you might encounter the usage of ‘more quiet.’ However, both forms are accepted, with ‘quieter’ being more commonly used in everyday conversation.